I've had ApplePay for 6 months and have only been in one store that uses it.
Blame it on the US' ancient banking infrastructure. I'm in Canada and the challenge is finding a place that does not accept ApplePay. It's accepted pretty much everywhere, ranging from big retail stores to the mom and pop corner store to the ice cream truck in the park. If they can accept debit, then odds are very high that they accept tap payments which means they can take ApplePay.