Just guessing:
Apple doesn't want to pay the high price of a premium/small chip that they need for NFC?
Apple wants their 30% cut from someone in that financial chain (Visa, stores, middleman) Or cut out the middle man completely. They are trying to figure out a way to get a cut of the comission and the credit card/processing companies are saying "no way".
Long term it will hurt them if they dont get in on the action.
The credit card skimmers are scary enough. Imagine someone placing a NFC reader 'under the counter' (behind the counter, hidden by junk) and it's 1 ft from the real NFC scanner and it just starts picking up everything. They can break the encrption later. Hell, behind the counter, they can even plug the device in for power/Wifi and the employees will have no idea what it is. I have no idea how NFC stuff works, so correct me if the security is bullet proof, but I doubt it.