Being a non-drinker (no alcohol ever), I used to think that the culture of heavy drinking (or smoking pot) was normal.
I had no idea how these things worked, and I always dreaded the parties. Coz it always constituted an interrogation of the non-drinkers/smokers (i.e. me). It started with an apparently friendly conversation about why I never drink, and as soon as I say that I’ve never had a drink it becomes a full blown shit-storm.
I’ve worked at a big corporation earlier and nobody ever bothered me about it, but startups are full of kids trying to drown their insecurities in alcohol, and they’re more than happy to lend you a hand (or a bottle).