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.
I don't buy the reasons they say why we don't have a CDMA version of the Nexus 4. What I get from the reasons is that Google would have to make like 77 devices, just for the US but Apple has their system closed and does not have 77 version of the Iphone 5, yet we see CDMA and LTE. WHAT IS REALLY GOING ON?