T-Mobile USA has been hit with hard times since the iPhone sparked the second smartphone generation, and particularly since the failed AT&T buyout of the company for its spectrum. While T-Mobile does have various high-end devices (such as the Nexus 4 and Samsung Galaxy S III) it is missing the iPhone in its lineup.
The iPhone is notoriously taxing on the assets of carriers: while it does draw customers in, it is also expensive for the carriers. It is so expensive, in fact, that Sprint offering the iPhone was supposedly one of the hardest draws on that company’s limited financial resources. So while iPhone customers do end up being a net benefit for carriers, the initial shock of offering the device can overwhelm the financials of less-stable institutions. Ironically, T-Mobile USA is very public about how they would like to offer the iPhone, but that the “economics [would] have to be right.” T-Mobile USA has ever begun rolling out iPhone-friendly 3G bands in select cities, hoping to draw the (limited) amount of unlocked iPhone users to their low-price network.
T-Mobile’s future is uncertain here in the United States: as such, it only makes sense that the company doesn’t want to make a brash decision which could ultimately bankrupt the corporation. And, honestly, Apple doesn’t need T-Mobile, having the three largest US telecommunication corporations, and various smaller carriers, already offering their flagship device.