[averysmallbird]

Your general premise is valid, but the specific theory doesn’t fit the relationship between the merchants and the credit card companies. See the fight over the Durbin/Marshall swipe fees bill: http://merchantspaymentscoalition.com/merchants-support-sena...

But your point about support — eg reversibility and fraud prevention — is very valid. Credit cards aren’t merely transactions in databases, but a set of customers and services.