I think the key word is debt when bills state "for all debts, public and private." (And a couple more categories under the law. [0])

At the moment you're asking for the drink, you are not in debt to the coffee shop, they're setting a precondition on an exchange. [1] Now, you might have a case if they let you run up a tab...

[0] https://www.law.cornell.edu/uscode/text/31/5103

[1] Yes, there are a positive number of milliseconds where somebody owes somebody something, but pedantic software intuitions don't always apply to law, and overall that's a good thing.

> This note is legal tender for all debts, public and private.

See also USC §5103:

> United States coins and currency [...] are legal tender for all debts, public charges, taxes, and dues.

Thus a private person is only obligated to accept cash as repayment for a debt, not for purchases.

Companies simply get ahead of that law by refusing to provide the service or good.

Works in retail bc at the till they can just say 'no cash no business deal'

Doesn't work in other ventures so easily.

It is along the lines of 'we reserve the right to refuse business to anyone'