"A sign of desperation is the ever-increasing lower shift in hysteria over lost "childhood."

When all the talking heads are arguing that a 17 year old Britney is being "sexualized," or that 17 year olds who have children are "babies having babies," then we see that they are resisting by pushing back against those who were recognizably adults in previous generations.

* A little wild speculation *

I think that this is a reaction towards loss of ownership over adult children.

200 years ago it was virtually unthinkable that a young man's career path and choice of spouse would've been his own to make against his parents wishes."

Hardly. It was very thinkable, and common.
1814. Boys went to seek their fortune in London and Dublin, they went to seek fortunes in Kentucky and Far West, they went to sea and to army, and got jobs out of home as footmen or scullions.

Young men were commonly separated from their living parents by weeks of letter travel time, if the parents even could read. And if the parents were poor labourers without large purse strings to hold then they did not have much legal power to control the boy´s career and marriage choices from a distance.

Independent adults left to sink or swim far from help or control of parents were common. There were plenty of success stories with their own farm in Indiana or a shop in London. There were also a plenty of failure stories at poorhouses and Tyburn Tree.

By and large, it seems that the young adults were perfectly aware of the thinkability and attractions of independence. They just thought that it was useful to enjoy support of allies like parents, if practical.