Some folks were too busy studying in college, to socialize much... let alone to drink. I see this from the other side presently, as a college professor. My students spend every waking moment on HW/studying, projects, or part-time jobs. Most commute. There are no frats, and very little campus social life.
So then these fine folks graduate, going to work for Boeing or Lockheed or whatnot (aerospace engineering context here). Then what? What sort of social life awaits them? They're saving every penny (remember, these are engineers), learning about investment, advancing their careers, maybe doing grad school part-time. Or helping their younger siblings, elderly parents and so on.
The point: ours is a socially broken society. We don't have the Old World convivial social gatherings, whether that Old World is in Europe or Asia or wherever else. We're atomized. We study, we work, we retire - and then what? In a better world, we'd have viable social interactions outside of immediate family and outside of work. Because... if you neither work anymore, nor have family,... what's left? Meetup.com?