There's nothing about QR codes that necessitates what you're talking about. Apple Pay and Google Pay could have easily worked using QR codes rather than NFC.

There's nothing about QR codes that necessitates what you're talking about. Apple Pay and Google Pay could have easily worked using QR codes rather than NFC. The cash register would just need a QR code that was an encoded JSON payload that included the amount to be charged, a merchant name, and a merchant ID. You'd scan it using your chose payments app and the app would say something like "You're about to pay $13 to Bob's Burgers. Approve?" and you click Yes and you're done.