Visa and Mastercard are taking a 3-4% cut of every single consumer payment made in much of the world. That ends up being a very, very big number.
There are two assumptions you are making, both of which are false. The first is that handling cash isn't expensive, but it is. You have to store in various secure locations, transport it between those locations, count it multiple times... And that's true even if you're a market trader or a small shop. For those people it could easily be a significant part of their day and a significant risk, all of which goes away with cards (and the fee is nowhere near 3-4%, it's more like 1-2%).
The second is that, in a market that has demonstrated a willingness to accept the transaction fees of the major card providers, that anyone would "leave money on the table". Sure they'll undercut them initially to win market share but once they have it, the price will inexorably creep back up to the level the market will bear.
My assumptions are based in that I’ve worked in the industry. There’s plenty of small restaurants that are cash only, because they operate on the thinnest of margins. Gas stations as well. To the merchant, a fee of 3% + .10c per transaction is very common. More for Amex.
The second point sounds like an economics 101 conclusion. Network effects are real. Regulatory capture is real. Starting a new card network is harder than beating google in ad revenue in search.
not saying it is the case but a lot of restaurants I worked were cash only because their supply chain was very low tech (also cash-only) and they simply didn't pay the taxes.
Gas stations might be higher at least in the USA because the kick back for gas is sometimes higher (e.g.: 1% cash back). Also, gas stations seem to really don't want to handle cash those days.
There are two assumptions you are making, both of which are false. The first is that handling cash isn't expensive, but it is. You have to store in various secure locations, transport it between those locations, count it multiple times... And that's true even if you're a market trader or a small shop. For those people it could easily be a significant part of their day and a significant risk, all of which goes away with cards (and the fee is nowhere near 3-4%, it's more like 1-2%).
The second is that, in a market that has demonstrated a willingness to accept the transaction fees of the major card providers, that anyone would "leave money on the table". Sure they'll undercut them initially to win market share but once they have it, the price will inexorably creep back up to the level the market will bear.