I think you might be underestimating how some people type really slowly when given a full sized QWERTY keyboard, numpad and all.

Then again the one limiting factor of phone keyboards (touch or physical) is that they’re designed for two thumbs, instead of just whatever fingers happen to be closer to the button you want. Though I’ll admit I do miss when Nokia, BlackBerry, etc, came up with unique solutions for how to get a small physical keyboard attached to a phone.