There are practical reasons why having NFC payments tied to your phone aren't a good idea.
When you reach the till in a supermarket, chances are, you've no idea how much the final bill will be, NFC payments are currently limited to £20 (I think), so, when it comes to paying, you're probably not sure whether you'll be able to pay with a contactless method, or have to enter your pin. Therefore, you're more likely to fish out your card, that can pay either way, than your phone, which won't work for larger values. Unless you're one of those wonderful people who waits until the last possible moment before fishing out your purse from the bottom of a tardis-like handbag.
The low limit on contactless payments means you will still have to carry a card with you, unless you live your entire life buying less than £20 worth of stuff at a time.
Then there is the lack of adoption, currently, of contactless terminals. The shops that could afford to replace their terminals (supermarkets, department stores, large retail chains) are those that you are likely to spend too much in one transaction to be able use them. Smaller retailers, independents, corner shops etc can't afford to swap out expensive equipment just to accommodate people who want to buy a paper with their phones.
Next is convenience. You may say that using a phone to pay is no more inconvenient than a card. I disagree. Not sure how Apple Pay will work, but, with NFC on my Nexus the screen has to be active in order for NFC to work. This is a good thing, as it prevents drive-by payments attacks. Taking a phone out, turning on the phone and then swiping is less convenient than just waving a plastic card. If you have just one contactless card in your wallet, you don't even have to take it out to use it. If you need to use the fingerpint scanner on an iPhone in order to use NFC (which would make sense if you want security) then you will have to master the art of holding your phone, pressing on the scanner and holding your shopping all at the same time (being able to scan your fingerprint with the phone held upside down would make that easier, can the scanner read upside down fingerprints?).
All in all, the miniscule amount of time saved by waving a card instead of entering a pin is negligible. Compared to the time taken to travel to a shop, find what you want, queue at the tills, wait for your items to be scanned, wait for the terminal to connect to the banks (for those retailers without permanent connections) and for the assistant to ask if you want cashback, those 2 seconds you save are nothing.
Maybe the reason that NFC payments have failed to take off so far is not down to the technology or the brand on the phone, it's that, in the end, a lack of security of having no authorisation on plastic cards is worrying and adding a layer of security by tying the payment to a phone that needs authorisation removes the very convenience of not using a chip and pin.