I use the SAME credit card on my Samsung Pay for almost all my transactions and it has been working fine EVERYWHERE until Walmart alone started blocking it recently.
Remember these platforms (Samsung Pay, Apple Pay, etc) rely on integrity of their operations. It’s possible that there are vulnerabilities they are trying to protect against for the same reason you’re railing against WalMart; most of the public associates breaches with a vendor, not the actual card processor which is usually the point of compromise.