That's really just a personal trait. I love going to my kid's friend's birthdays because we get to talk to the other parents who have become good friends as well, plus we don't have to look after the kids as much. "Adult time" and we know they're having fun. I don't have to drink in those.
I guess not everyone is that outgoing and not every parent group is as friendly as mine but it's hard to see getting drunk as a necessary counter to that.
> Turns out people suck at socialising without alcohol, and if alcohol disappears, people just stay at home and play video games or something.
Again, a personal trait. It's extremely common here in Brazil to drink but it's also very common to just not drink and have as much fun. Someone saying they need to have alcohol to enjoy themselves at a gathering is not going to be looked at very kindly, as if everyone else was just so boring they had to intoxicate themselves to bear through it.