Wait, have you never paid cash at a gas station before?
You go up to the teller, tell him which pump your car is in, and get your $2 back.
You go up to the teller, tell him which pump your car is in, and get your $2 back.
They could take cash automatically like a vending machine but that's going to require new staff to go around and collect money and deposit it. Probably much more expensive than taking credit cards.
The market will decide if it's more expensive. Customers exist who will commute to another charger so they can pay cash. If the money left on the table is more than the cost of the cash module and attendant, it will be adopted.
That seems to actually be a distinct possibility. Some people seem to use cash so infrequently they forget it even exists.