Because T-Mobile is a company that actually knows how to handle customer service and tends to value its customers and employees highly; a practice that is almost antithetical to TelCo business.
The complete culture-incompatibility the two companies have would destroy the value of any purchase.
I agree T-Mobile has stellar customer service, I contacted them about poor coverage in a new area I moved to. Got a $40 credit on my line, and within a month a network technician had fixed the issue and brought my coverage up.
It's amazing the difference though, I'd call Verizon and would get a generic "We'll send someone to check on it" months later nothing would change. It's nice to be with a company that will actually do something about your problems.
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?
