^This.
The banks can't restrict what you're allowed to buy with your money (be it credit card, debit card, your own deposit(s), or any funds at your disposal).
They CAN sell dedicated products like mortgages, but it's explicitly defined and the clients know the purpose of the loan.
I've just checked the terms for CC in my local bank, and there's nothing about what product(s) and/or service(s) that can be purchased. It defines general operations that can be peerformed with the card: ATM withdrawal, POS payment, transfer from CC account.
it amounts to a partial blockade IMO.