This isn't a modern society thing, it's not an MTV thing, it's a biology thing. Unless those Amish are feeding their kids growth hormones they aren't mature when they reach 13. Maybe they're better behaved, maybe they're more responsible, maybe they've got more responsiblity. But they aren't mature.
And maybe I experience a different class of 13 year old kids than you folks do, but the kids I know do 6-8 hours of homework a night between their various sports activities and are already thinking about what college they're going to go to. I'm sure lazy slobs exist at 13, but not all 13 year olds are lazy slobs.