As dminor said, it was part of the agreement, but more to the point, you don't always necessarily know when you're taking the card. You'd only see the fee afte

As dminor said, it was part of the agreement, but more to the point, you don't always necessarily know when you're taking the card. You'd only see the fee after running the purchase. IIRC, there was some way to decipher some 'types' of cards (airmiles reward card vs free gas vs cash back cards, etc) by some of the prefix numbers, but I don't think that was reliable, nor feasible. It's been a couple years since I discussed this with my bank's merchant account person, but in a nutshell it was "you don't now until after you take the card how much it'll cost you". There was a base fee, and most cards would fall in to that - 2.1% in my case, IIRC. But, if someone used some 'get 2% cash back on all purchases!' card, I'd be charged 4.1% (again, IIRC, might have been a bit more or less). When you don't know what the price is going to be, you end up needing to err on the high side, and factor in higher overall fees to every price, raising the price for everyone along the way. And the banks make more money because the whole 'free air miles!!!!' mentality gets people to use their card more. The banks get their fees on a per transaction cost (and interest on balances that carry on month to month) - the merchants effectively paid for all your 'free air miles'.