Scott Greenfield links to and comments on a New York Times article describing the unwillingness of young people to "grow up."
Adolescence is extending well into a person's 30s. It's not hard to explain while: Lifespans are increasing.
Any Fantasy literature fan would tell you that elves are the most playful species because of their long life cycles. If you're going to live to be 1,000, why "grow up" at 50?
When life expectancy was 30, 13-year olds were serious business.
There's a very good chance that people in my generation (who don't eat themselves to death) will live to be 100.
And so what we're observing isn't a nefarious cultural trend: It's simply a rational response to changing longevity. Thirty is not middle-aged, and for some might not even be quarter-aged. Relatively speaking, a 30-year-old still is a child.
And for another take on the issue, see here:
"They're going to have to grow up eventually!" First, I hear contempt in your voice, like you can't wait till they have to suffer. That's narcissism. Get that out of you, why should you be happy that they're going to suffer?
What is so great about adulthood that you'd wish it onto someone?