> Well you have to deal with American and European financial regulations, KYC, &c. - you have to vet merchants, you have to run the infrastructure to process transactions, refunds, direct payments from bank accounts to pay for cards, and all of those things. Those are real, genuine business activities that are non-negotiable and while they may seem simple, in practice they are not at all simple.

Those are partially or completely taken over not by the card network but by the bank that is issuing you the card, so a change in the underlying technology will be transparent.