The problem was that vendors tended to make arbitrary minimum fees for using cards which in no way reflected the actual fees they were paying. Smaller stores were steering customers to cash as it was easier to under-declare earnings with cash. In response Amex in Australia reduced their fees to stores while simultaneously reducing the value of their awards points programmes (since those were ultimately funded by the fees being charged.)

This also plays into application stores - since developers often don’t pass on fee reductions (such as the subscription fee reduction of 30%->15% after 1 year.)