I get it that there's multiple reasons they wouldn't want to and they can say it's their policy, etc but it's on the paper money itself "LEGAL tender for ALL debts public and PRIVATE".
It's like when you hear the stories about people paying debts with buckets of coins. Obviously a huge PitA but technically allowed.
> Section 31 U.S.C. 5103, entitled "Legal tender," states: "United States coins and currency [including Federal Reserve notes and circulating notes of Federal Reserve Banks and national banks] are legal tender for all debts, public charges, taxes, and dues." This statute means that all U.S. money as identified above is a valid and legal offer of payment for debts when tendered to a creditor.
That taco shop that doesn't want to deal with cash isn't a creditor.
And everywhere else in the U.S. if the Payment Choice Act passes.
https://www.cashmatters.org/blog/america-legislates-for-cash
https://www.congress.gov/bill/117th-congress/house-bill/4395
Edit: Those jurisdictions have "pro-cash legislation" according to the ATM Industry Association Stateside Monitoring Service, but the source appears paywalled:
Went to a concert in SF at the Independent last month and the bartenders wouldn't take cash. You're saying they were breaking the law?
If you look at the edge cases, it becomes more clear why the federal government doesn't require businesses to accept paper cash. Imagine someone attempting to purchase a sky scraper in Manhattan with cash. That would be a mountain of bills which would be unwieldy to carry, transport, and count. Or what about if someone insisted on buying your house with all pennies. Would you like being required to accept that payment?
The idea that cash shouldn't create an undue burden to a business is an important one. And that's why the federal government doesn't require the acceptance of cash for transactions. It's best to let the parties involved decide what method of payment is most appropriate.
As for the burden: if taking money is a burden, why are you in business to begin with?
If they make you pay before giving you the food, then they can refuse to take cash.
The legal tender law is about what forms of payment can validly settle a debt denominated in US currency.
That is a far cry from "what must businesses accept in daily consumer purchases".
Congress could likely force businesses to accept all forms of legal tender, but hasn't.
However, a store owner can choose to only accept bottle caps or conch shells in exchange for their goods if that's what they want to do. If you go up to the register and you tell them you want the widget, you have to pay whatever they're asking in exchange. Doesn't have to be cash, credit or even money of any sort.
As an aside, our currency used to say that they could be exchanged for the denomination in Gold (or silver, depending on the note) on demand at the US treasury.