And yet, before the 60's and before the rise of proper education, teenagers went to work after elementary school (if that) and became mature, responsible adults much sooner. At least, so I heard. They couldn't get together and have orgies or whatever, because they were expected to be either at work, or back at work at 6 AM.
Work now requires more education. A PhD student is not less mature than a bachelors student just because he's in school for more years. He doesn't lose the right to make decisions for himself.
Prolonging the socially defined period of childhood didn't magically rewire brain chemistry.
[/faux history teacher]