There are many reasons. Many of them are covered in a 4 part series on the
General Lack of Creativity. But let's get nasty today and blame someone else: like school and institutions alike. (by the term "school" I mean primary and secondary school, that is to say everything that is more or less compulsory and comes before University, which is another matter indeed)
I know, I know... I'm spreading negativity instead of love... It is not positive or constructive to throw blame around, but some things need to be said!

Many students, especially those who are poor, intuitively know what the schools do for them. They school them to confuse process and substance. Once these become blurred, a new logic is assumed: the more treatment there is, the better are the results; or, escalation leads to success. The pupil is thereby "schooled" to confuse teaching with learning, grade advancement with education, a diploma with competence, and fluency with the ability to say something new. His imagination is "schooled" to accept service in place of value. Medical treatment is mistaken for health care, social work for the improvement of community life, police protection for safety, military poise for national security, the rat race for productive work. Health, learning, dignity, independence, and creative endeavor are defined as little more than the performance of the institutions which claim to serve these ends, and their improvement is made to depend on allocating more resources to the management of hospitals, schools, and other agencies in question.
Ivan Illich, Deschooling Society
School is first and foremost an institution. It should not be confused with education. For education has been around since the beginning of times while schools are in place only since a short while - more exactly: since the industrial revolution. And they haven't change much since. We'll see that shortly. It is precisely its nature of institution that generates many of its flaws. Every institution has a goal of doing something; the goal of a hospital is healing people, the goal of police is secure safety of the citizens, the goal of schools is supposed to be educating children. But every institution, even the local brass band, has a goal that comes before anything else and that is its own perpetuation and longevity. It is an unwritten rule of every institution to stay active and prosper. That it is why it is not in the interest of the police to eliminate crime and it is not in the interest of school to find a good model of education. Many jobs rely on things being wrong. It would be really stupid of any "scientist" to publish conclusive results on the age of the famous
Shroud of Turin. Not as long as the cash for "research" keeps flowing.
So, around the times of industrial revolution some factory owners realized that the production of goods could be far more efficient if their workers knew how to read and do some basic calculus. Their practical view was supported by the views of classical antiquity (especially ancient Greek), which values logical deduction and rhetoric abilities above anything else. Studying Greek art, sciences and philosophies was very fashionable at that time. Before long a curriculum was established and schools were made compulsory to satisfy the needs of so many factories.
Don't get me wrong, not everything is bad. Enlightenment brought about many fantastic things; development of true science being only one of them. We would not have medical science, hospitals, pharmacy, physics, chemistry or anything like that without the mental breakthroughs of the enlightenment. The idea of compulsory schooling expanded the pool of talents. There would be no Tesla, Edison, Einstein or Fleming if the poor children wouldn't be obliged to go to school. The problem is, that we still stick to the same concepts that were established at the time when schooling was conceived. The world has moved on since then. So should education.
The idea of academic abilities is only one of them. It simply states that math, language and some encyclopedic knowledge are worth more than all other pursuits of the mind. What about arts? Dances? Music? Could you look Beethoven in the eyes and explain him that his creativity is worth less simply because is in the field of music and not philosophy?
That is
de jure, de facto is far worse.
Recent neurological research proves what has been intuitively known for ages; your brain and your body will develop to meet the needs and challenges of (early) childhood. There are many well documented cases, when a child has become blind on one or both eyes, simply because it's eyes were closed or covered during the
critical period within which the neurons ("sensors") in the eyes were supposed to develop. Child's developing body assumed those neurons will not be needed so the child remained blind for the rest of its life, despite having otherwise perfectly normal visual apparatus.
On the other hand we can look at the early life of
Usain Bolt. I have heard anecdotes which are yet to be confirmed (if you could find me good sources of either confirmation or denial, please send me links or emails), BUT they are illustrative enough even if they are not exactly true. So, I have heard at one neurological lecture, that Usain has been playing football (soccer, for US readers) on a meadow field close to his house and that meadow has been located on the top of a cliff. Underneath the cliff there was sea. The meadow had been leaning towards the edge of the cliff at a smaller angle which caused Usain's ball to run away quite frequently... If the ball reached the edge of the cliff before Usain, it was lost in the ocean. So young Usain had to develop some good sprinting abilities at a very young age. His developing body assumed this will be its task of survival so every muscle developed in a way to favor fast sprinting runs. That is obvious, you might say. What is usually forgotten is that also his brain, which actually controls those fabulous muscles and bones also had to develop specialized ways to do the job. Not only his muscles, his brain is made for 100m running just as well!
Whatever is trained and repeated in early childhood will stay there for ever. Every political system that used early childhood indoctrination knew that. It is absolutely necessary to start at early age to become a master at almost anything you can name; ballet, chess, math or music are just the most famous examples. The complexity of those activities can be mastered only if it is approached by a young and highly plastic brain. After the age of 7 most of the important brain connections are already fixed... Much can still be done, but surely it is not the same is if it were started a few years earlier. It is of an utmost importance to give child's brain as much practice as it can handle. If that child also shows emotional affection (passion) for that activity, that alone can lead to a magnificent career. The bottom line is that brain needs to practice that activity trough all of the critical periods; early childhood (3-7), young childhood (7-12) and teen age (12-18). After that it is more or less time to harvest the results of hard work. Learning gets harder and harder with each passing year. This is the hard reality as told by contemporary neuroscience.
Are we doing anything to take advantage of those facts? Not really. Most of our children are spared "hard" mental work until the age of 7. I put the word "hard" in quotation marks, because that "hard" work should be presented and experienced in the form of relaxed playful activities that is suited for child's age. I am not speaking of child's labor. Well, many good opportunities are missed... But many more are to be lost in years that follow.
Because if you think about it, is it really math, languages and memory that children practice at school the most? (I say memory, because most of other subjects, like history, geography and even chemistry require nothing more than good memorial skills to be passed) Is it really that they practice those skills? What
skills (I can't emphasize that word, skills, hard enough) do they practice? Only one: passing exams! It could be either oral or written exams, by the time you reach 16, you are a master of solving math puzzles, filling blanks at language tests, naming 5 things of this or that, manipulating teacher's feelings when being put in front of the blackboard, etc... Or simply cheating at any of that. These are the skills that you practice over and over again. Beside obedience, indifference and passivity but that is another matter (read
this book) indeed. The point I'm trying to make is, that your brain specializes in an entirely narrow and useless field. On the side of that you acquire tons of "knowledge", that is to say, useless data that can be used only in solving crossword puzzles or TV quizzes (and you forget most of it when you get out of the school anyway). Instead of learning skills of creativity and productive thinking you really learn some very limited skills by doing whatever is needed to achieve that one and only goal of passing exams. Unless you had been active on your own or with help of your parents, your brain remains underdeveloped in every other field or activity for ever. By the time you reach University (most of them are much better at educating than compulsory schools because they give more freedom to teachers), your brain has already lost most of its valuable plasticity. Just as muscles in your hand will deteriorate with time if you don't use them, so will parts of your mind. The more time passes the more hard it is to reanimate them. After a certain point it becomes impossible and there is no return. Our schools fail to exercise the vast majority our mind, so most of our mental capacities are stunted in development, never to be reborn. It does not mean we should do everything at once, it means doing one thing passionately enough so that it includes everything else. Playing violin really passionately already includes doing math, arts, dance, history, biology or anything else you can think of, but this time, in a service of beautiful music, which makes learning all those supportive fields so much more exciting. Each child should find its own passion and learn everything else to support it. Which introduces us to the next problem.
Schools have a growing need to be standardized. Everything has to be sorted within standards. Children are sorted in classrooms by their age - I know you take that for granted, simply because you are born into this world without ever being any different - but step back and think about it. Is it really their production date that is the most important factor of classification? Some children are more advanced in math, some in dance... Wouldn't then follow that advanced math children should practice math with older students with matching abilities? 7 year old
Jose Raul Capablanca played chess against adults because no other child was as good a match for him. And even the sheer number of children in one such class is usually too big for quality learning (usually around 30, sometimes even more).
Secondly; why should textbooks be the same for everybody? In music schools where there is no such standardization a good teacher can choose from a huge number of books for his students to adjust the needs of each particular one. There is only one reason for this hard standardization and that is to meet the needs of a large industry which produces those books: professors (authors), publishers, printing facilities, bookstores and many other institutions rely deeply on "new and revised" editions that are compulsory sold every year by state law. Even if you borrow, somebody had to buy it first. Most parents go nearly broke every September but there is no need for that. At the end, it is about money on both sides. Does basic algebra really change so much with every passing year? And more importantly: does one size really fit all?
If you really think everything trough - what is at the heart of an education? What is that minimum that is needed for this activity? Is it a "new and revised" edition of a textbook? Not really, a good teacher could do even better without. Is it a classroom? No - we could do well without that either... I think that at the heart of it all is a teacher and a student or better to say - a relationship they develop. And that has been cluttered by tons of administration burden, standards, forms, tests, merits, levels, standardized textbooks, or whatever you can name that keeps this schooling industry running and jobs safely kept... It is not just money, sometimes these standards are put in place with very noble causes but also without a view of a bigger picture (see
Barry Schwartz on this issue). As a result, teachers are preoccupied with administration so they rarely have time to focus on teaching, and children are preoccupied with tests and scores so they can't focus on learning. Whatever is truly individual and worthy in one person is smashed down and washed away by these standards which fit a rare few and exclude everyone else. That is the reality of today's schooling. That is why the majority of the people feel dumb and excluded in schools or after they finish it. That is why they feel untalented. That is why all those creative and smart children (whose parents can't stop talking about) grow up to be depressive and boring adults. It is important to understand that this is not a result of any vicious conspiracy; it just came to be this way by many small steps which all made the majority sink just a little deeper into their comfort zone. They made grounds to open more institutions (commissions, boards, research labs, panels...), make more jobs, make everybody a little happier and at the same time everything a little worse, so more jobs can be made to correct it. Concepts like "
Tragedy of the Commons" can play a big role here. I don't believe they are doing it consciously. They are not that smart. Perhaps nobody is.
OK, let's review that process once again: at the age of 7 children in most developed countries are put into classrooms and told to sit down and be quiet. Otherwise teacher might get a headache and no one wants that, does it? But again, if you really think deeply - isn't that the most unnatural thing you could do? Look at baby kittens or puppies. Are they sitting still? No, they are jumping around and playing... very much like human offspring of the same relative age. Schooling uses different techniques to petrify children; threats, punishments, emotional blackmail... If anything of that fails, they assume the child has ADHD and they put it on Ritalin. Childhood education should fit the needs of children not the needs of teachers. Sitting still and listening is an activity of the old.
Obviously, at the age of 10-12, when hormones kick in, most children become sick of school. They have had enough of standards, they intuitively feel there could be more to life, and that this system does not fit their intellectual needs. They start to hate the idea of education and mental effort in general, simply because it was presented to them in the wrong form - in the form of schooling. They rebel! (in every other way, education and mental effort remain being fun - even factory workers like to solve crossword puzzles, don't they)
From here on (this is highly speculative, but bare with me), schooling has two different strategies to keep them in order. First predominantly works on girls and calmer boys, second works mostly on boys and wilder girls.
At the beginning of early adolescence (as we said, when hormones kick in), 5 million years of evolution starts to reveal itself. Most girls calm down and act more responsibly. That is the necessity of becoming a mother! (in the eyes of adults girls seem to mature faster than boys, but in reality they just mature in different way) However, most boys become even harder to control, they take greater risks, they damage things around them and often even themselves in games they play. That is the necessity of becoming a hunter! What they need is a rabbit to be killed and brought home with its head chopped off. Our bodies are not developed for writing homework and answering emails. Our bodies are made to survive in nature and it is impossible to understand psychology without internalizing this hard fact. It is only a small fraction of percent of the entire evolution that we have been living in what we think of is a civilized society. The vast 99,9999...% of the time which shaped us is during the time we were in wilderness.
So girls are usually bargained to suppress their individuality with good grades and compliments. After all, it is a system that values very highly sitting still and behaving well, especially combined with responsible attitude towards homeworks and school assignments. This are all the qualities of a young (soon to be) mother. They prosper trough schooling, many without getting any real education and many of them finish on positions that require high level of responsibility and obedience (they can become even a judge or a medical doctor..., but more often a secretary or a nurse).
Young hunters are a harder case for school. They will just not sit still, listen, obey or behave. They will not learn or sometimes they will hide their knowledge just to show rebellious attitude. School has a number of readily available mechanisms for such young brats; school detentions, punishments, principal's office hearings, bad grades, letters to parents, emotional blackmail, and so on... In most cases they succeed to crush rebellious spirit by the age of 18. Unknowingly they also destroy his/hers own individuality. What it is left (in both cases) is an
average person (whatever that is).
But rebellious spirit is at the heart of creation. Some sorts of rebellion should be nurtured and cultivated into a positive form which will question dogmas or conventions and at the end produce something new and better (I have a feeling someone just doesn't want that... even in healthy families it takes parents with a very big heart to teach children to question authority, that is themselves [parents] in the first place). Oscar Wilde reminds us:
Disobedience, in the eyes of anyone who has read history, is man’s original virtue. It is through disobedience that progress has been made, through disobedience and through rebellion.
but also:
Most personalities have been obliged to be rebels. Half their strength has been wasted in friction. Byron’s personality, for instance, was terribly wasted in its battle with the stupidity, and hypocrisy, and Philistinism of the English. Such battles do not always intensify strength: they often exaggerate weakness. Byron was never able to give us what he might have given us. Shelley escaped better. Like Byron, he got out of England as soon as possible. But he was not so well known. If the English had had any idea of what a great poet he really was, they would have fallen on him with tooth and nail, and made his life as unbearable to him as they possibly could. But he was not a remarkable figure in society, and consequently he escaped, to a certain degree. Still, even in Shelley the note of rebellion is sometimes too strong. The note of the perfect personality is not rebellion, but peace.
(my emphasis... taken from the essay
The Soul of Man Under Socialism)
There is another mechanism how degrade young geniuses: give them extra homework. "
You are smart, you should do these extra hard exercises too!" But you know, these kids are not stupid - why work double if all you get at the end is the same "5" (or "A" in US) as you would otherwise? Isn't it better to hide among the average and pass smoothly without lifting but a finger? When nobody mocks you for sticking your neck out? Sure it is... Being average it is! But that kid has still lots of spare energy (remember; puppies like to jump around, not sit still), and if it is not transfered with his hobbies or sports into something productive, it could be very well turned against him/her-self in a form of a violence, drug abuse... it could even lead to suicide. (I didn't come up with this - a far more experienced elderly teacher told me to write this down)
In all cases the system that is based on standardization has managed to produce a product of its own kind: a standard human fit for a standard job. Or, as George Carlin puts it: an obedient worker. Unfortunately many of them finish as boring, anemic and frustrated teachers (or textbook writers, headmasters, social workers, etc) who fail to inspire children for arts or sciences (or whatever else). Even more so; they manage to present these fabulous pursuits as disgusting. The cycle is closed and the schooling business continues. If anyone remains creative or positively individualistic it is in spite of schooling, not because of it.
So what is the solution out of this mess? Firstly; we should demolish this system and think of a new one where the constructive relation between the teacher and a pupil will be at the heart of it. We only add things from which their relationship will benefit. It could very well be textbooks and standards too, but only when needed and as needed. But above all, it should be a system in which skills are transfered, not encyclopedic knowledge. If I aspire to be a photographer, a fireman, or even a judge, or a medical doctor - the first thing I need are skills of the profession. It could be skills with equipment (camera, computer...) or skills of any other kind (social skills, mental skills, you name it). And don't worry, I will gather encyclopedic knowledge, but this time, not so much by memorizing as by doing. Books are good way to learn, but only in supplement to practical training. And of course, a good and experienced mentor who is guiding that process is also critical. It looks like we have a triangle; at one corner is practical learning, on second theory (books) and finally mentor on third. I have a good sense that the Renaissance knew that. The greatest masters of that time; Donatello, Raphael, Leonardo, Michelangelo, Vasari, Galileo and many others gained that knowledge with practical work under the careful and caring eyes of the master. If they entered the workshop at 10 or 12, they were masters themselves by the age of 18 or 20 (todays graduates are beginners at 22). And guess what; they were all rebellious in spirit too.

But the Medici, who payed for everything, were smart enough to see beyond attitude - they saw and nurtured the talent! And that is how they calmed them down!
References and further reading/watching/listening:
Ivan Illich - Deschooling societyJohn Gatto: Dumbing us downJeff Hawkins: On Intelligence (find him also at
TED Talks)
This
talk by Ken RobinsonRSA animated talk by Ken Robinson (find him also at
TED Talks)
Also all of the books by Ken Robinson... please read them all!
Richard Dawkins -
The Selfish Gene (or anything else by him... it is all brilliant)
Dan Ariely:
Predictably Irrational - find him at TED too
Oscar Wilde:
The Soul of Man Under Socialism)
a lot of stuff at Wikipedia, Google, and so on... I heard a lot of that in person during lectures or interviews... to many to name them all.