Money and payment settlement systems are not the same thing, although you could be forgiven for believing that. I use a credit card for 99% of my transaction volume, and credit cards are not money. The fact that the notional value of the transaction is denominated in dollars doesn't mean I am actually using dollars as the medium of exchange--the exchange is facilitated by a clearinghouse and my individual transaction may not even result in a transfer of money (actual dollars) between parties, if there is an offsetting transaction (or chain of transactions) within the same settlement period.