You have hit the nail directly on the head.
However, the trend is continuing: Drinking ages have been raised to 21. Drivers licenses are held back 'till 17. Marriage ages in many states has been pushed back. Furthermore, 14 and 15 yr olds have been handed a world of sophistication, but are expected to tread water until they reach a legal age or accomplish a certain academic level.
On another front, this man made construct is also a result of parents who are unable to let go of their "babies". The same parents that do everything but teach their children to be self capable and self responsible.
And there are more of those out there than you think.