In the basic self-service lounge, this is ridiculous and offensive. I'd make sure management was aware of my opinion on the matter. Not that my opinion matters much, but if they get a steady stream of complaints, maybe they'll rethink the policy.

I've been to a few lounges with some form of table service or a full-service bartender where they were making cocktails to order. In that case, I'm fine adding a tip to a room charge. Odd thing is - in those lounges, I can't recall any kind of awkward request to tip. It was just a standard room-charge form with a tip line if there was a charge. No pressure to tip if there wasn't a room charge.