That’s arguably not a great example, since there are both more than one international credit/debit card networks, and even these have been subject to constant regulatory scrutiny.
There was a time when common wisdom was that telephone companies and many other infrastructure businesses needed to “obviously” be monopolies as well (sometimes state-owned, sometimes private, which is arguably the worst of both worlds). I really wouldn’t want to go back to that.
> That’s arguably not a great example, since there are both more than one international credit/debit card networks, and even these have been subject to constant regulatory scrutiny.
The two cards are essentially interchangeable so it is a duopoly. And the fact that they are subject to constant regulatory scrutiny without adding laws to force new entrants is why it is such a good example, it shows how well regulations can work without adding competition. To me in Europe credit cards works really great with low fees and no fuzz, I don't think that anything needs to be done about that more than is already done.
To card issuing banks, absolutely not. Visa and Mastercard compete for their business.
To merchants, yes, since they can't reasonably only accept one but not the other, as that would turn away a large fraction of their customer base. This is why most regulatory action happens here.
> subject to constant regulatory scrutiny without adding laws to force new entrants
There are absolutely measures taken to encourage new market entrants or at least more competition among the existing ones. (Whether they are effective is a different question.)
As one example, in the US, every debit card issuer is obliged to add at least one other brand/network to their cards, so that merchants do in fact have some routing choice. In Europe, some countries also have a domestic competing debit scheme, such as CB in France, Girocard in Germany etc.
> I don't think that anything needs to be done about that more than is already done.
I think you underestimate how unstable the current equilibrium is. The interchange cap regulation is relatively new, and I doubt that the networks will fail to come up with other ways to grow their market share and/or revenue that will, at some point, require further regulatory scrutiny.
There was a time when common wisdom was that telephone companies and many other infrastructure businesses needed to “obviously” be monopolies as well (sometimes state-owned, sometimes private, which is arguably the worst of both worlds). I really wouldn’t want to go back to that.