As Chris2048 said, I believe the law draws a distinction between buying something and paying a debt. I've heard that, for instance, you can always use cash at a sit down resturant where you pay at the end because that's paying a debt, but if you order the food (or whatever) up front that's not a debt yet, so they don't have to accept cash.

It's an interesting distinction that I only learned about recently, and I'm not sure I agree, but it seems to be the compromise we currently run off of.

> “Legal tender for all debts public and private” used to mean something...

That's a myth. From the US Treasury Dept. (https://www.treasury.gov/resource-center/faqs/currency/pages...):

"[31 U.S.C. 5103] means that all United States money as identified above are a valid and legal offer of payment for debts when tendered to a creditor. There is, however, no Federal statute mandating that a private business, a person or an organization must accept currency or coins as for payment for goods and/or services."

Buying a taco isn't repaying a debt..