Quite interesting topic, perhaps those who have been banned from casinos it has been because managed to make a deal with supernatural beings, so they always pocket a good money out the casino and get away with it. 
Haha, that's one wild theory! Lol. I guess if someone always walks out a winner, people start thinking there's more than just luck or skill at play. But realistically, casinos (physical casinos) are quick to notice patterns that hurt their bottom line. Whether it's card counting or just a lucky streak, they'll find a way to shut it down, no supernatural contract needed.