The reason we use qwerty on a smartphone is extremely straightforward: people tend to know where to look for the keys already, so it's easy to adopt to even though it's not "efficient". We know it better than we know the positions of letters in the alphabet. You can easily see the difference if you're ever presented with an onscreen keyboard that's in alphabetical order instead of qwerty (TVs do this a lot, for some reason, and it's a different physical input method but alpha order really does make you have to stop and hunt). It slows you down quite a bit.
That's definitely a good reason why, but perhaps if iOS or Android were to research what the best layout is for typical touch screen typing and release that as a new default, people would find it quite quick to learn a second layout and soon get just the benefits?
After all, with TVs I've had the same experience as you with the annoying alphabetical keyboard, but we type into they maybe a couple of times a year, or maybe once in 5 years, whereas if we changed our phone keyboard layout we'd likely get used to it quite quickly.
Even if not going so far as to push it as a new default for all users (I'm willing to accept the possibility that I'm speaking for myself as the kind of geeky person who wouldn't mind the initial inconvenience of a new kb layout if it meant saving time in the long run, and that maybe a large majority of people would just hate it too much to be willing to give it a chance), they could at least figure out what the best layout is (maybe this has been studied and decided already, by somebody?) and offer that as an option for us geeks.
Even most technically-minded people still use QWERTY on full-size computer keyboards despite it being a terrible layout for a number of reasons. I really doubt a new, nonstandard keyboard would get much if any traction on phones.
It only worked because it had to, given phones just had keypads back then. As soon as qwerty-with-your-thumbs was available, everyone abandoned T9 and never looked back.
