You use touchscreens to turn on your headlights because it is cheaper, touchscreens and embedded SoCs are so cheap these days that adding one to your car (as long as it is rectangular) is tons cheaper than wiring multiple buttons on your dashboard.

The cost of programming those displays is relatively small and fixed, it doesn't get more expensive if you sell 1 million cars or 10. But these companies still haven't managed to have proper processes for the software platforms for their cars so the software ends up sucking.

They treat their cars like video game developers, once done and released there might be a few patches. But the next car is mostly rebuilding the software from scratch.

On an aside as more people are becoming aware that buttons and knobs are actually nice you will likely see them coming back, but only on the more expensive vehicles.