Haha IDK it's not like there's some set universal rules for this stuff and you get executed by the high committee if you play differently, you're just supposed to have fun! At least that's my take on it.
IDK about the US, but I think this wouldn't actually be legal anywhere. In Portugal, for example, there's some rules about this, even for personal consumption. I didn't read anything about gerbils in particular but it's not necessarily as straight-forward as just buying some animals, killing, and cooking them. It's because of public health laws.
Well being naked is embarrassing, so I would think most people don't really want to undress in front of others.
Regarding drinking games: it's kinda like "I lose the game, but at least I get to drink!". This way everyone has fun even if you're losing. The winners can still drink even if they win anyways, it's just not mandatory like for the losers.
Is someone about to be murdered by the CIA?