[thaumasiotes]

I've experienced one party held at my (then) employer's premises. Alcohol (as I recall, mainly wine) was consumed. I don't drink.

There was thanksgiving food; there was cake; a few people brought small children; my boss played an instrument and sang for us. It was great.

Basically I agree with you that the "party" described was lame. The problem isn't that there was beer at an on-premises party even though OP doesn't drink. The problem is (definitely) tacit mandatoriness and (to a much lesser extent) that the party didn't have anything to offer other than a chance to show that you're "dedicated".