Have to say, from my UK perspectve, if I want to pay someone I can do that straight from my account to theirs. I can understand avoiding a processing fee. But for me, transfers are without charge.Honestly, thinking about checks is instructive as to why AP is not as prominent as one might expect. There is a massive convivence gulf between writing a check and any type of credit card payment (swipe, chip, or tap). With plastic, you quickly interact with a terminal. Writing a check means retrieving a checkbook and a pen, filling in the details, waiting for the final cost, filling that in, and then having the check scanned by a clerk.
The difference between tapping a card and tapping a phone is quite small. It took years and years for checks to become uncommon payment methods in stores, despite the large benefits of plastic. It will take far longer for phone/watch payments to really become the standard.
FWIW, I do still write checks under certain circumstances. Just yesterday I paid a contractor with a check, as using a card came with a 3% processing fee. That's a couple hundred dollars. Looking at my checkbook, it seems I write one or two per year.