It's not about playing a sound on release. It's about feeling where the button is in the first place. When you place your finger on the screen, you can't tell where on the screen your finder landed without looking. It's much easier to feel for and grab a knob and turn it or a physical button and push it, than it is to accurately place your finger on a screen and keep it in the same position for repeat actions (especially on a more bumpy road).

On my car stereo, for example, I have 6 buttons for pre-programmed stations: [1][2][3][4][5][6]

Without looking, I can put my finger just to the left of [1] and select a station by feeling my way across. There is no way to do that with an in-dash touch screen without looking. Maybe you could play a sound to designate which button your finger is currently on, but what if you don't want to press that particular button (i.e. you land on [2] and you want to select [3] instead, but -oops- a bump in the road caused momentary disconnect between your finger and the screen [make no mistake, this sort of thing happens often])? Then you need a way to "confirm" a selection, and we're back to the original problem.