I had the situation once where a newish hostie brought the after-landing drink onto the flight deck while on finals. You can imagine the questions if there had been an accident. Two empty glasses and the deck smelling of booze. "Take them back". Ref the question of taxying, I think most people used the rule of: after parking brake on and engines shut down. In fact, if it was a hotel stop, the drinks didn't arrive until in the taxi. Mind you, that was the better part of thirty years ago.