Do you know what would be better than CarPlay? An open protocol. It's my phone and my car, why do I need both companies' blessings for connecting them?
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.
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.