Across most of the world, Mastercard/Visa has used various threat tactics to basically tell merchants that if they charge a card fee they'll get banned from mastercard/visa.

Obviously for most businesses, thats a death knell, so most capitulate.

And the few places with competing payment methods (eg. Kaspi in Kazakhstan), Mastercard/Visa have ~zero fees, and sometimes even negative fees (eg. "special offer, you get half price use of the subway if you have a mastercard")