Something overlooked in the real world that encourages the maintenance of private payment systems (cash) is th existence of a large number of people with bad credit.
Bad credit or no credit. Having no record in the credit databases is as good as have negative entries, for many purposes.
About 20% of the US population has neither credit cards nor checking accounts. Some of this is because of personal preference but a lot of it is because these people can't handle something as abstract as a checking account without wrecking it.
A significant part of this is that banks have simply moved out of a lot of neighboorhoods, and checking accounts are simply not easily available. Many people grow up without interaction with the banking system, and therefore don't get electronified. Eric