The big thing for me is that the lifetime of a car is a lot longer than the technology development lifecycle.

I just bought a 10 year old Toyota estate (station wagon). It's got a reasonable screen and Bluetooth implementation etc. But I'm never going to want to use the built in navigation because it's just not as good as what my phone will do. And the audio integration isn't as sophisticated as it might be - I have to choose the app on my phone.

Whereas CarPlay/AndroidAuto is generic from the car point of view, and as phone features and software improve your car capability evolves too.

I’m sure the car manufacturers would much prefer if you updated your car as often as you do your phone.