[tomkarlo]

I suspect this is less about the credit risk of the cardholders than the risk of unrecoverable fraud, although there's also the theoretical risk of some kind of fraudulent conveyance by the card holder.

Fraud: I steal someone's credit card and use it to buy crypto, then move that currency somewhere unrecoverable. The card company is unable to recover anything. (This can be mitigated by recovering from the exchange in some cases.)

Fraudulent conveyance: Holder maxes out all their credit cards buying crypto, hides it, then claims bankruptcy. Card companies can't recover anything. (Yes, you could do this with something like gold, but it would be a lot harder to hide and sell later on.)