However if I happen to have an Apple device it's by far and away the easiest (and most secure) way for me to pay. And yes, I do prioritize places that take Apple Pay over those that do not.

There are lots of iPhone users and often business can getting better (lower) processing fees by accepting more secure methods like Apple pay so if it's literally just flipping a switch and possibly paying a bit less for processing why wouldn't a business do it?