Discriminations harms extend well beyond those which are recognised legally. The law itself is very often a tool for further oppression, and should be considered on that basis.

There are two elements to that question: the legal and the moral.

Legally the premise is shaky as it's a short walk from "use a specific payment method" (a financial instrument, a device, a service, a company) to what are protected classes: age, race, national origin, religious beliefs, gender, disability, pregnancy, and veteran status in the United States.[1] As such, strictly as a business decision there's a considerable risk involved that such practices would be found to be de facto discimination against one or more protected classes.

(Keep in mind that there are religions which consider interest on money to be against their beliefs, which would then transfer to use of revolving credit instruments. I've no idea whether this has been tested in US courts.)

On a moral basis, even that which is not strictly illegal may be against principles of greater justice, and gatekeeping access to goods or services can easily work against those with limited means (unable to buy the latest mobile smartphone or desktop/laptop computer), unabile to maintain broadband comms access, owning a working but end-of-lifed device (for Android as little as 2--3 years, somewhat better for Apple), living in regions without high-speed broadband (most of the US), excluded from access to credit by low credit scores, or forced by circumstances to accept massive invasions of privacy or exposure to manipulation (propaganda, advertising, targeted manipulation) simply to participate minimally in the everyday business of life.

Note that remote-commerce can be a force for inclusion and against oppression. The Sears Roebuck Catalogue was the subject of recent commentary on that point, see for example:

"How Sears Catalog Fought White Supremacists" https://www.voanews.com/a/usa_all-about-america_how-sears-ca...

The major operative factor to me seems to be whether a technology constrains or expands opportunities. Reducing payment options quite clearly constrains them.

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Notes:

1. https://www.legalmatch.com/law-library/article/protected-cla...