I'm between cruise contracts at the moment, and while there isnt a no drinking policy with the company i work for, there are strict limits on how much you can drink. Certainly this is so you can play to the required standard, but as a member of the ships company, if there is any form of emergency on board, at any time of night or day, you have to be able to respond and help the guests, which you can't do if you're passed out from drink in your cabin.