I was kind of with you up until here. Radios at least are modular in most cars so you can just swap them out. I wouldn't be too surprised if everything else was designed this way at most car manufacturers but with a proprietary module system. Many seem to pick one or two design languages and at that point the buttons need to be designed one or two times.

Redesigned how, 90% of cars look the same, and it's been industry standard for years.