The reason they do the dial is for safety reasons, they don't think reaching and touching a screen is safe when driving-- they want your eyes on the road..
As the owner of a Mazda3 with a control knob resting directly under my right hand when it's on the arm rest, I can say that it's easier to control than a touch screen. I never push the wrong button, I don't have to move my arm, and I don't have to constantly clean fingerprints off the screen. When I drive another car with a standard touchscreen, I really dislike it.
