Have you considered that some things are deeply entrenched because they work?

I think most people who aren't teetotalers and who have worked at a startup have brought beer or whiskey to the workplace for after a long day, and I don't think that it's that different when the boss brings the beer: if you are working with people you can't trust, you probably have other issues.

Nobody's saying you have to drink, but it's not a tragedy if that leaves you out of some of the benefits of social drinking.