They might, for instance, give card-holders some virtual slot cash or something, and they can't keep track of who should and shouldn't get it. Yes, it's the same for bingo and slots, but that's the point.
You should probably look into the rules in WI for reversing a self-ban, as if I were the casino, I wouldn't give you a card that could be used for slots with a ban in place either. It would depend on the regulations in your jurisdiction, but generally speaking, no, you don't have any particular right to a player's card, or to enter the casino at all.
