I agree that the idea is good, but I feel like it can be achieved just fine with a local-only form-filler, if it isn't already (all browsers and password managers now offer to save credit cards, and Apple & Google Pay even handle actual payment processing with better fraud protection).

The bootstrapping problem seems like something of their own doing, both because it's a server-side solution as opposed to client-side, but also because there's most likely rent-seeking and extra fees involved. Every merchant wants to make more money so they should've had near-complete coverage very quickly unless there's a significant downside for the merchant for participating in said system.