From the article:
But increased profit from credit card customers is not the only reason to raise prices for those who pay with plastic. As more people use cash to save at the pump, they are forced to come inside the store to pay, which creates another opportunity for the gas station owner.
"Because while you're in there, you're going to also pick up a coffee, a soda, maybe even a sandwich," Mount said.
I've always said that "pay at the pump" is a convenience that I appreciate, but from a business standpoint, it was probably the dumbest idea ever implemented by the industry. I wonder how much money they (convenience stores) have lost over the years by allowing customers to pay at the pump instead of coming into the store, where more than likely they would have bought something else in addition to the gas.