You're right in that with a physical control you still probably glance at it as you're reaching for it, but you don't have to keep your eyes on it the whole time unlike a touch screen. With a touch-screen there's no feedback that your finger is on the button and that you have actually pressed it. With a physical control, button, knob, or slider once you have your hand on it you can manipulate it without looking. They demand momentary glances, not seconds of constant focus.

Well, it depends on button and function. Rarely used functions will require looking, common ones (assuming button placement is sensible) will not, but even ones that require looking are still better because you skip going thru the menu to find it.