Do you believe that is really the reason car makers refuse to implement CarPlay? It does feel strange, this stubborness, I can't see how the can deliver the best technical solution for their customers without implementing CarPlay and Android Auto.
Are they imagining there is more value in this than there is? Am I simply underestimating the value potential for having their own thing? Do they want to protect their customer's data? Do they think that NOT having it somehow is a positive differentiator? Do they not know how to make it happen? I am stumped.