Isn't the value of CarPlay/AndroidAuto indirect? As in that the value is coming from the data being generated to enable better mapping? Because the truth is that some of these mapping services' main utilities depend on a large network of users (e.g. information about congestion, road notices, etc[0]). In that way it seems beneficial to get your app onto as many vehicles as possible and even gives motivation for making CarPlay cross-platform (even if the main benefits only go to Apple users).
[0] Also, wtf AndroidAuto. You pull data from Waze users for things like speed traps, road hazzards, etc, but you don't let me contribute when using Auto? Why is there no button (or voice command) "report road hazard"? Hell, this'll even help you classify events for your ML models.