They're quite difficult to use without looking at them, and I've got better things to look at while driving. Better buttons that don't move and have "presence" than I can feel without looking.
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In my first car, I could operate the windows, climate control and sound system without taking my eyes off the road at all, although I had to glance briefly at the (fixed) display to see what radio station I was tuned to if it wasn’t obvious.
Those controls are typically on some surface of the car your hand is braced on. They're also very simple physical controls with a good amount of tactile feedback. It's hard to fuck up a simple push button window control or AC dial. Even on a bumpy road you'd be hard pressed to have trouble with such controls.