I feel like card competition is actually pretty steep. MasterCard and Visa may have the majority of the market, but there are still Discover and AmEx. I have been using things like NerdWallet to figure out what is the best card to go with, it is usually a healthy balance. I think the main thing is that most Debit cards are Visa or MasterCard...and you are locked in by your bank. Where as credit & charge cards are a free for all.
When it comes to advertising online though, you have only 2 choices...Google or Facebook. As a business I can't not go with those two or I'll lose immense business. I can go with a Visa, Mastercard, Discover, Amex...and it really has no effect on me outside of the benefits the card gives me. The fees charged to the banks, etc are essentially the same. So it's really no comparison as to which is worse for the market itself.
You’re talking about different things. When you shop credit card offers, you are comparing issuers (eg Chase vs Capital One). That’s not the same as the payment processor aka card network (Visa vs MasterCard).
Of course it’s endlessly more complicated then that but it’s important to make the distinction.
When you open a web shop, you pay to get SDK from payment processor to integrate them with the site.
When customer clicks “Checkout”, they are sent to payment processor website to enter card number like 1234 ...5678... and whichever card it is, it goes through, and shop owner receive the payment later.
Which means payment processor has contracts and connects with every card networks, absorb API differences, and on top of that, obeys and agrees to everything CC network thinks or says, to be able to handle any cards customers may have with them.
So if a Visa or MasterCard exec thinks maybe he don’t like Cheetos and make a call to processor CEOs how they think about it, no later than by Friday no one will be able to order a single bag of Cheetos, especially online, using any credit card because payment processors will have explicitly communicated that Cheetos had never been tolerated from the beginning and any store who let that happen will have accounts frozen.
It happens somewhat softer than that but kind of happening once couple years these days.
When it comes to advertising online though, you have only 2 choices...Google or Facebook. As a business I can't not go with those two or I'll lose immense business. I can go with a Visa, Mastercard, Discover, Amex...and it really has no effect on me outside of the benefits the card gives me. The fees charged to the banks, etc are essentially the same. So it's really no comparison as to which is worse for the market itself.