BM thrives as an ecosystem. When you gather with your friends to play a boardgame, it's not just the game itself that contributes to the mirth, but also getting to know your friends better through social interaction outside the boundaries and characters of the game. If everyone restricted their interaction to purely within the boardgame, I doubt the night would be as fun.
Yes, social interaction takes potential time and energy away from focusing on the boardgame itself, but without it people may simply choose to not come at all.
