Increasingly common at smaller businesses in western Washington (have seen this in Seattle, Bellingham, and occasionally elsewhere).

Even where it's "technically" possible, it's becoming more difficult. Some grocery stores around here don't staff traditional teller lanes at night, shrinking down to only self-checkout, which are card-only machines. To pay cash, you'll have to escalate to the roaming attendant (or at least, I assume they can find some way to accept cash for that transaction? I can't say I've tried)

Restaurants in big cities and sports stadiums. It's called a cost saving effort, but with restaurants especially it's usually to discourage poor people from trying to come in.

I think some theme parks have started. Not accepting cash should be illegal, and certain places have started implementing laws that make the practice illegal. There are various reasons why a person is unable to have a bank account.

I've seen retail businesses in NYC and NJ that were no cash. I think NYC has banned that practice, but I'm not sure if that has held.