Comment by codewiz

Hidden fees remove any consumer-side pressure on credit cards to lower their costs.

It also creates perverse incentives for cards to pass part of the merchant fees back to the consumer as rewards or even cash. Here in the US, 2-3% cash back is typical, driving consumers to prefer credit over other payment methods.

Meanwhile, merchants are forced to bake the fees into the retail price, causing the paradox that those who pay upfront end up spending more for the same goods.