I'm not talking of people who prefer, most of the time, to socialise with friends outside of work. That's probably healthy and normal.
But I've come across some people who, on some kind of point of principle, refuse to entertain the idea of going to any social event that's work related or to even to just go for a casual drink with a colleague after work. I even know a guy who boasted that in 30 years working he had never been to a retirement do, a promotion celebration or an office Christmas party. He seemed to think that was some kind of admirable achievement.
AIBU to think that it's a bit of a silly position to take and there's no harm in occasionally going to the pub with colleagues to wish someone well in their retirement or even just to have a wind down and a laugh with people you spend so much time with in a work related setting?