Not just US. Take for example Germany, the largest country in EU and most places are cash-only. Although due to coronavirus adoption of different payment methods (apple pay, contactless, card, etc) has been increasing.
I'd actually be curious about the numbers/actual ratio. I can't think of a single chain of stores that takes cash only, which will make up a huge percentage. On the other hand, restaurants, food stalls, ... are hit and miss.
That's different though. It's one thing to only support ancient tech for cashless payment and another to stay cash-only. I wouldn't call that backwards. It's just a choice.
What is wrong with cash? It is one of the most fail proof form of payment. Stripe fail, chip fail, NFC fail, internet connection fail, phone line fail. But cash work almost all the time.
In last year, I have bailed out quite a few people stuck in the checkout lines because whatever hi tech form of payment, they were using, didn’t work and had no cash.
I live in Norway, and cannot remember the last time my card wouldn't work - period. Not just with the reasons stated.
When I lived in the states and worked retail, your cash wouldn't be accepted at a lot of stores if the power was out (or if internet/phone lines caused the registers to fail). To complicate things, I worked in a pharmacy, so accepting cash for the medicine without it going through the system might have actually been illegal.
You have to remember to get it out of the ATM. I ran out of cash like a week or two ago and have been too lazy or forgetful to stop by an ATM to get it.
Not to mention to use an ATM you need a card already to begin with, might as well just pay with that card directly?
In Switzerland we have both. You can pay cash nearly everywhere, or contact less, or using our own transaction system 'twint' usually over the phone linked to any bank account (or even prepaid kinda like PayPal)