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, maybe a ghost giving them signals at the roulette table? Lol 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.While for some gamblers, they'll simply think of it that guy probably really has someone on its back supernaturally guiding to the wins that he's getting.
Anyway, we all know that it's unlikely to have that guy and it only happens in the movies.