When I go to college football games I drive by the fraternities on my way to park. I'll see quite a few folks sitting on the front lawn seriously messed up. Usually a buddy or girlfriend standing or sitting with them keeping an eye on them.
I'm older so at the old people bars or parties, you just don't see folks drink them self into that state. I assume that sort of filters out to the sad drunk bars / folks at home as you age. I didn't get it when I was college, I don't get it now, that doesn't look fun.
They must think their classmates are drinking a lot, but it's pretty clear it's not nearly as much as they think, as most of their classmates seem capable of carrying on a conversation and standing up... meanwhile they are not.