Google announced a mobile payment strategy today that will allow consumers to pay for stuff by tapping their phones on a specific terminal at retailers.

Industry watchers have long expected phone platform providers like Google, Apple, and Nokia to get into the payments business, exploiting a set of wireless technologies known as near-field communication. NFC World has a great rundown of the big questions to ask about how the new payment system will be structured and how that will affect the current payments industry.

I can't help but wonder, though, if the biggest question remains unanswered: why would people use their phones to pay for things if they have perfectly acceptable alternatives already? Cash works. Credit cards work. Debit cards work. Online payments strike me as a space far more in need of innovation than retail, where, by definition, you're already standing in front of the payment machine.

This may be a case where the technology exists, so insurgent companies are looking for ways to use it to disrupt the incumbents. It seems to me that simply swapping out one form of easy payment for another isn't going to get Google very far in developed markets. Maybe Google Wallet could work in conjunction with "reward cards, coupons, tickets and transit passes" -- and that would be the combination that would sway consumers.

Still, count me among the skeptical. Out of the billions of people with cell phones in the world, something like 100 million people worldwide use some form of "contactless" payment, but only a few million here in the U.S., according to the analyst firm, Gartner. And it isn't really a technological problem, as NFC already works.