Who can't get a card? Anyone should be able to get a prepaid debit card, although it is a bit of extra hassle. Those work on the Visa / MasterCard networks, and are accepted by any business (except perhaps certain hotels and online services).
Cards require bank accounts, and bank accounts require home addresses. Not shelters, not PO boxes, not halfway houses. Home addresses. That takes out a large number of people who likely need banking services the most.
