But this is exactly my point. Those apps exist, and are popular. But they can't use NFC because of Apple's limitations on hardware APIs. So, QR payments are popular.
All those apps would use NFC for many of those use cases if they could. Which brings us back to the start of this discussion: which use case has QR payment, but not NFC (and thus requiring a camera in addition to a NFC chip in a smart watch)? Answer: the huge (international) market of non-NFC payment/ticketing apps.
A trust box, for example. Or a simple donation option. The ticket (pay what you want) at my favorite punk gig in town. Etc.
In e.g. the Netherlands, the majority of payments go via a payment system iDeal¹. Its easy to start an ideal payment with a QR code. It's, by my knowledge, impossible to do so via NFC - other than via Apple Pay or Google Wallet.
Then, there are vast fleets of phones out there that don't even have NFC. I wouldn't be suprised if a majority of phones in use today don't have nfc chips on board.
And, a large section of the population won't switch on NFC even. For battery. For privacy, for fear etc. If not for scanning my glucose meter, I would've switched off NFC by default. I'm no tinfoil hat, but 30+ years of software development and hackery has kept me weary of such stuff.
All those apps would use NFC for many of those use cases if they could. Which brings us back to the start of this discussion: which use case has QR payment, but not NFC (and thus requiring a camera in addition to a NFC chip in a smart watch)? Answer: the huge (international) market of non-NFC payment/ticketing apps.