(Broad generalization incoming) Before the industrial revolution, teens would have spent most of their time around adults (like their parents), and very little time exclusively around people their own age.
Populations were distributed more broadly...kids were expected to work at a younger age...no phone or Internet...apprenticeships at a young age were common...
I guess they still had a few other opportunities...school, picnics, sports, swimming down at the creek, church, civic youth groups, summer camp, etc...
Most of these are also pretty modern things. Long education and leisure time did not exist for most people until somewhere around ons hundred years ago, depending on where you lived. Stuff like boy scouts was not invented until the beginning of the 20th century and it took time for them to become popular across social classes.
Some historian argue that even childhood is a modern invention.
Older generations doubt the ability of the young to "get things right"...to keep the society they are familiar with on track...
Younger generations, with fresh eyes, wonder how older generations let things "go so wrong"...with an eye toward improving the society they've inherited...
An excellent book, Lila: An Inquiry Into Morals, by Robert Pirsig, explores this and other phenomena in great depth...
It's a semi-sequel to Zen and the Art of Motorcycle Maintenance...
I recommend it...
https://en.wikipedia.org/wiki/Emerging_adulthood_and_early_a...