Why use NFC when you can use the more widely available Bluetooth 4.0?? Think about all the iPhones that already have it?? That's million of 4S's already out in the wild plus the millions of "new iphones" they're about to sell this fall!!
Apple never does something until its better than what's already out there so instead of following the NFC tech that everybody seems to add to phones but noone seems to use, why not just do it with the low power Bluetooth 4.0??
That's just my .02
Bluetooth needs to be paired and doesnt support mobile payments, its not as quick. Different uses