Being a student used to mean being a teen, and that gives maybe a decade to party before the biological clock starts ringing and nobody can party all night because they have little kids. Sure, outliers always existed, but they were rare. Post teens were adults with adult incomes but not adult responsibilities, like kids, for quite a few years, usually.
The modern economic strategy of extending childhood by about a decade by extending education and eliminating entry level positions and near elimination of the high school grad career path has all kinds of fascinating economic effect, mostly bad, but one big effect is by the time the advanced degrees and internships are done and someone finally has an above poverty level income and medical insurance and a place to live other than parents house, the biological clock is ringing and if you don't immediately start popping out newborns, you aren't going to have biological time to do it, thus dramatically limited party culture.
So lets say culturally theres a shift from the delay between "I graduated and now I'm an adult" and "I got a herd of kids and after school stuff to attend and kids sports and ..." used to be a decade and now its maybe two years? So you'd naturally expect a decline of maybe 80% in party culture, taking it from dominant activity in the 20s to its basically gone?
There is also the biological effect that scenes from the movie "Animal House" look like fun to a teenage brain, maybe not so much to an older brain, so increasing the drinking age and dramatically criminalizing drinking while also socially pushing the mantra often heard on HN that its impossible to socialize (party) without being an alcoholic (which is criminalized) will result in a natural decline in party culture.
Hmm, not sure I agree with that really.
I agree with most of your sentiment about elimination of entry-level jobs and extended education, but I think the natural response (and the response we see) is for women to have children at older ages (https://en.wikipedia.org/wiki/Advanced_maternal_age).
It used to be the case that you'd graduate high school and start having children in your early 20s, so I'm not sure I agree that there was ever a time when it was "socially acceptable" to be an adult with an adult income and no children for several years.
Yeah that would be meetup.com