IMO They (Visa et al) have been desperately clinging to the outside of their speeding gravy train for way too long, and it's only a matter of time before they run out of track underneath them, so they're trying every trick in the book to keep things running.

Any new competitor could spell the end for them, so making it astronomically difficult to onboard enough people is so far working out for them.

Exactly. Courts will ask why they can charge high fees and not lose customers. The answer will be that they are anticompetitive or behaving as a cartel or monopoly would.