I'm guessing what you really meant was "prerogative?"
So far: Yes.
Not being an Android developer, myself, I'm not certain. But, being an experienced software developer, myself, all I can say is "It's just software." If they wanted to work with Google and OEMs to Find A Way, I'm confident they could do so. Some sort of "authenticated carrier plug-in" to the OS, I'm thinking.
Except VZW and "at&t" don't really need it quite so badly as does TMO, do they? Besides: There's more to it than the device side. There's also the "WiFi as cell tower" side of it, too. TMO invested in that infrastructure as an inexpensive way to mitigate against their sorely lacking footprint. VZW and "at&t" have not.
You don't think connectivity problems or being unable to use their chosen device(s) might not affect customers' decision to stay or leave? I know it would affect mine. In fact: It was Sprint's declining network performance that provided the impetus for me to move my wife and I over. Now, here we are, on T-Mobile, and I'm liking them.
But the phones we're using are apparently stuck at 4.0.3 (ICS), with neither the OEM nor TMO showing any inclination for future updates (never mind they broke hands free calling on the last update, promised to fix it, and have not); many of the areas in which I want/need to use a wireless phone have marginal-to-non-existent coverage, and many of the most interesting (to me, anyway) new devices aren't supported by TMO.
So what do you suppose might happen, some day, if I reach a point where, "uncarrier," as wonderful as I feel it is, must give way to the importance of actually being able to use an up-to-date device on their network?
T-Mobile is aware this problem exists. They have acknowledged they get regular requests to address it. All I'm saying is they need to get off the dime on it, or it will, eventually, bite them.