When the hell is it necessary?
For example, when I was working in Scotland at a dysfunctional company where nobody could talk straight about what was so fucked up about the place while they were in the building. The employees started going to the pub once a week after work and it was like floodgates opening. The few of us who had worked in better studios could tell all the fresh-out-of-school noobs who'd moved up to the godforsaken middle of nowhere thinking that this was the job that would make their careers, that this wasn't how it had to be. We could meet up with guys who'd been unexpectedly fired and help them find other gigs, and they could help the ones who were stuck and looking to get out.
Granted, I could have thumbed my nose and ordered a coke every time, but the fact is that every little thing like that has an effect on camaraderie, and I would rather choose my battles. If I had alcoholics in the family, though, it might have been worth it because it would have been more emotional cost to drink than to be an oddball and not drink.
