Apple products are so popular, it's no wonder that they rolled out a CDMA version of the iPhone 5. Verizon & Sprint cover a pretty large swath of the US population. CDMA is also going the way of the dodo, so that's another reason why Google wouldn't necessarily invest those funds into a network technology that will (relatively) soon no longer be supported.

Keep in mind that this year Apple actually *increased* the number of different versions of their popular iPhone with the iPhone 5. It's all about accommodating the marketplace in a way that creates revenue.