That's in fact one of the pros of carplay/android auto as opposed to just putting your phone in one of those windscreen attached holders; you get to use the volume buttons on the steering wheel. Annoyingly my car doesn't have play/pause buttons on there, but if it had, they would work.

Even on the holder, you'd use Bluetooth, and those buttons work. With Android Auto/CarPlay you can also use a joystick, if your car has one.