People come back to it because to be playing it properly, you'll always be playing with friends. Not playing it properly, though, are the people who hop from regiment to regiment, not really making any true friends, and then either quitting altogether or moving on to leading their own regiment, which somehow often ends up with tons of members before it disbands.
People come back because no one who played in a regiment for a good amount of time didn't have at least one amazing moment with those people. It's a game you can laugh at, with friends, and equally be super competitive about. It fits a lot of sub-audiences in the audience that plays this sort of game.
"Community" is too broad. Everyone should have a reason to hate "the community" by now, if they've been around for long enough. It's the community that they're in that they like, whether it be an immediate, regiment level, or bigger, like the regiments that they always fight with/against.