I think the most important thing school does, for me at least, is giving a set goal to meet. It forces you to study to get around these hurdles called "test" or "angry teachers." It gives those hours spent studying (piles of books on your desks, papers everywhere, deadlines tomorrow, video games still calling) a purpose. Even if it's boring you still have to do it. Even if you hate what you're studying, even if its usefulness is still an invisible blip in the distance, you've still got to do it.
Someone once told me that 80% of what you do doesn't have much impact on your work (as in, useless). But those 20% won't happen unless you do those 80%. It's a pretty pessimistic view, but I think it rolls. School and daily jobs give you goals to force you to do those useless 80% instead of only dreaming up all the 20%.
To an artist without inspirations, a blank canvas is torture.
