It is not a good thing for consumers to be required to buy a specific manufacturer of device to make a credit card transaction, when the credit card number that had to be entered in the first place is in their other pocket.
Go abroad, your payment system doesn't work.
Battery dies, your payment system doesn't work.
iOS chooses a bad time to update/reboot, your payment system doesn't work.
The shop choose a rival system, your payment system doesn't work.
So you still have to carry the card anyway.
And, let's be honest, Apple know exactly who you are as they have your Apple ID on the same device. Just because they've not shown it linked in, doesn't mean they couldn't, can't, don't, haven't or won't. If you are authenticating the software on the device and the device is linked into an Apple ID account or course they know who you are. Whether they join the dots or not greatly depends on local legislation, not technical capability.
I'm actually much more interested to know how Apple will work at the business end. Because, for sure, every time I call them about the 100's of iPads my schools use, on the Mac Mini servers that we have, with the stupendously expensive MDM system we bought, they couldn't care less and literally do not want to know.
They are one of the few cloud providers to not provide an EU data protection guarantee for their cloud services (which technically means you shouldn't be using them in EU businesses like schools etc.). They are one of the least "business-friendly" companies that I've ever seen. Last time I rang up about a pupil iTunes account, it took 10 business days to reset and they were demanding original receipts showing the iPad serial number before they would touch it (despite being enrolled into our MDM and supervised by us) - security for home user, unnecessary hassle for verified businesses with tens of thousands of pounds worth of business with them. And we had to say literally dozens of times "No, we're a school, it's a school email, it's for a school pupil, it's a school device, we're a school".
I've also yet to see "other" payment systems that use the original credit card details separately in an auto-generated token with bank authorisation - that's the "new" thing, not that other payment systems don't exist (but, again, they aren't popular, even when they're cross-platform like the PayPal one I mentioned - I can show you any number of shops with the logo in London, but when you ask to do it, they have to go call the one guy who knows how and tell you "Never had a customer ask for this before", etc.).
Sorry, but even Android Pay is dead if you have to have it alongside Apple Pay etc. and you lock it to certain brands of phone. That's not a payment system, that's vendor lock-in. Either everyone has to take everything (e.g. like websites take Google Wallet, Amazon Payments, PayPal, WorldPay, etc.) or they have to take nothing.
And, I'm afraid, Apple just doesn't appeal to enough of the market to be the "one true payment system", no matter what gimmick they use, and they absolutely DO NOT co-operate with any other vendor whatsoever. They barely co-operate with some of their largest customers.
Like the whole "ID card" debacle... enjoy it while you can use your one type of phone in one particular location and look cool to your mates. Because, for sure, the next time you leave the city and travel outside, you'll realise that you need to pull out your card every moment still anyway.