Just to be clear, there is no statement from Apple or Google that Apple has blocked Google Maps or any other third party mapping from CarPlay. It could very well be Google just hasn't prioritized support.
I'm aware (and I'm sure Apple is aware) that Google Maps has more features. AFAIK Apple has never in their history thought that having the most features makes their product the best.
I'm also unsure Apple wants Maps to "beat" Google. My understanding is that based on a requirement for data from users as part of the licensing of Google Maps, Apple felt they're had to create and ship their own default maps app to preserve customer's privacy and default experience. That doesn't mean they're are against customers opting into a Google product.