I highly recommend everyone to read the book The Coddling of the American Mind. A large chunk of it is dedicated to this very question: why children have much l

I highly recommend everyone to read the book The Coddling of the American Mind. A large chunk of it is dedicated to this very question: why children have much less play time today than in the past, how it's harming them and what to do about it. Its conclusions are fairly counter-intuitive, but the reasoning is very convincing and backed up by lots of cited research.