Have you ever tried to steer something with a touch screen? They don't provide the physical feedback that helps people do the task.
There is much to be gained from using proven physical controls even if there is a computer responding to the user's actions.
I don’t like the touchscreen on my car radio. Actually I think it’s a step back in automotive safety. Now I have to take my eyes off the road to see if I am pressing on the correct area on the screen. With knobs and buttons, I could just feel where my fingers needed to be to work the controls.