_Handling_ cash is expensive. I never thought of that until my SO started working in a shop. To and from the bank, with stacks of coins and notes.. and there's presumably much more than that for larger firms.
In general I rely my statement on what merchants themselves are saying. Newspapers are writing interviews with merchants who (illegally) have stopped accepting cash, even though it's legal tender. "It's too expensive. It reduces our bottom line." That kind of thing. When I look around I see "Cards only" a lot of places.
The USA is not all the world. The US rules don't apply in other countries. Rules differ. In many countries _businesses_ have to accept legal tender. Including in my own. That's why it's such a big deal when businesses actually still refuse cash.
