I'm talking about the kind of people who have to choose between part of a shared apartment in a conveniently transit-connected part of SF/Manhattan, or their own studio/1-bedroom somewhere with low density and poor transit. Y'know, software engineers making $100k.
I don't live in the NY metro area but I visit several times a year since I got friends there. I always crash on the couch.
I vary rarely socialize with people with high income because, one, I grew up poor so most of my childhood friends are still below average in income but more importantly I find it very difficult to relate to people who grew up well off. Sometimes I hear my co-workers talk and I feel I am living on a different planet.
As far as shared housing, yes, 99% of college kids live in shared housing and the vast majority of them still socialize.
In a big house, the party often naturally squeezes into the kitchen, leaving the handful of introverts to sit quietly in the living room.