Pardon my ignorance, but physical cards are tap-to-pay since it exists, no smartphone needed, and as a bonus, you don't need to think about your battery dying before you need to buy something. It's a problem of extreme convenience, not something you depend on in any way. An alternative could also be a smartwatch, which you can set up tap-to-pay on, so you can have a custom ROM on your smartphone and pay with your wrist.

Why would I need a computer to do something that the computer that I already have in my hand can and should do?