https://www.nerdwallet.com/blog/credit-cards/credit-cards-ma...
https://www.nytimes.com/2016/03/27/your-money/credit-cards-e...
Merchants prefer cash as card costs them money.
Usually works with dry cleaners, cafes, etc. Big businesses generally say no.
I'm not sure if this is more prevalent in certain regions, because I never noticed it until I drove west from the east coast. First I was confused when I stopped at the cheapest gas station I saw somewhere in Nevada, only to discover it was cash/debit ONLY, and I think there was a 35-cent charge for using debit. After that, in California, I started noticing how easy it is to see the cash price when driving by, but you often have to look closely for the credit price.
It seems some states still ban it by law, though.