Google wants their services to be available on all US wireless carriers in the US, not just one. And however much they fail to demonstrate it sometimes, Google wants their services available in the rest of the world, too. Getting entangled in a particular wireless market would also be an issue.
If they bought/had control of T-Mobile why would that prevent Android phones from being sold on Verizon/AT&T/Sprint let alone on other carriers around the globe?
