It seems that most marketers and automotive interior designers live in another universe. I really, really want to ask them if they really thought that this is appropriate and why.

As was stated in another comments, it reduces the production cost. Screen is needed for navigation, so why not use it for other stuff?

And at least early on in the adoption of touch screens and probably somewhat still today the average consumer assumed touch screen was better because it was new.

Probably there is/was the "ooh shiny" factor of making everything be screens, and "ooh shiny!" sells/sold cars better than "ooh, functional!" which is also "ooh, looks outdated" in the mind of buyers of the last decade or so.

But after a while living with the stupid UX, the buyers would probably rather have the functional than the shiny.

"Now the screen is the button? Or is the screen not the button? I don't know! Maybe we'll all find out by the time when we're compacted like tuna fish in a can!"