If you have a credit line at the hotel, your Players' Card IS your credit card at the table, even today. Instead of signing a credit card voucher that says you promise to pay Visa, you sign a marker (check) that says you promise to pay back the casino. Not a big step to expand the idea of casino credit to all players who want it (and have a bank account)... credit lines are not promoted today but could easily be if society accepts it.

If I remember correctly, Caesars Palace even has a conventional credit card (Visa or Master Card) they offer to those who want Caesars logo on their everyday card. We're getting there!