I test drived a car days ago. I turned on the engine and the radio started playing pretty loud. I tried to turn it off because I wanted to listen to the car during the test and talk with the seller on the passenger seat. The two of us started fiddling with the touch screen and the buttons around it. He eventually managed to turn off the screen which had the side effect of turning off the radio. I joked about doing the same while driving and crashing into something while my eyes were where they shouldn't be.

Contrast that with the cars of a car sharing service I'm using. They have a big circular button with the usual on/off icon close to their screen, encircled by a volume gauge. You understand what it is as soon as you see it.