Maybe there's more regulation than I realise (and the emperor has more layers of clothes than Joey Tribbiani), but I'm not seeing it.
I assumed issuance of payment methods was much more strictly controlled than this due to the risk of contagion if the issuer can't meet it's obligations after the transaction (are card payments instant delivery between institutions these days? I always assumed there was a clearing period in the background).
Notably, these cards require online funds verification and settlement for every transaction. Some cards you might get through a bank or major card company may not, for convenience sake. But these cards do, for the obvious reason.
They're essentially pre-paid cards that load instantly (at the point of transaction) from a larger balance the dev/company controls.
There are even multiple APIs for creating card issuing APIs, checking account issuing APIs, etc. These have itemized pricing that looks more like AWS/GC/Azure pricing and are more complicated to use, in the same way AWS is more complicated than running everything on a single Digital ocean droplet.