For who? There are no other phone OSes for the car makers to bother caring about. They’re way way too small.

How can the car manufacturer cover their ass if your Blorg OS phone takes over the car infotainment and gauges and shows you complete bullshit.

Then you wrap your car around a pole, who is to blame?

This is why certification is needed on both sides for integration this deep.

Gauges I agree. Infotainment, who cares? It's not like CarPlay today is perfect. It routinely crashes on me mid-drive and requires a series of reboots to go back to working conditions.

Example: Having movies playing on infotainment wile the car is not parked is illegal in many countries, thus car companies want to make sure no 1st party integration will do that without the customer explicitly circumventing something.

If someone crashes when watching Alaskan Housewives or something on the infotainment screen, the car company wants to CYA by saying their system wasn't involved in the crash, it was an unauthorised 3rd party modification.