Some places drinking on the job would literally be a firing offence.   I've worked behind a bar and we were never allowed to have a drink even if a customer bought us one to join them.  Some very nice places would allow a long serving employee but the vast majority I dont think so.

Same applies to gambling, I doubt its allowed as it introduces complications and the question of bias or advantage.   If it was me personally and I was a blackjack dealer then that is the game I know best of all even while distracted.

  If Im out and in a casino thats the game I'd play, Im bad at learning new games fast and its then rarely profitable but a game you know off by heart from hours of dealing cards; arent you a master at that point and who doesnt like winning