Horace Dediu with the smartest take on why exactly Apple is (potentially) taking the mobile payments route after so many have failed in similar endeavors:
But one word of caution: if Apple does enable payments it’s important to realize that being a (payment) bit pipe is not a particularly profitable business. It will undoubtedly bind value to the iOS devices which make it possible, but I don’t think there will be a direct capture of profit from the transactions themselves.
So for a company that facilitates the payment clearing system, the margins are likely to be very thin and with costs being non-zero it may be nearly a wash. The real impact of the decision to support payments will be in the aura surrounding the iOS ecosystem. An aura which will glow intensely.
And an aura that will do even more to perpetuate lock-in to current hardware, which is where the real value is; not in facilitating your 99 cent cup of coffee. Makes a lot of sense.