I’m going to guess the reason might be that they have to keep up with Apple’s crazy yearly upgrades. It’s why software for iOS is so expensive, tends to go subscription, and is sometimes abandoned/orphaned. If my 2017 subaru no longer works with my iphone, I suspect we will replace the radio/display. Ours is tied to the backup cam but I’m hoping a new one can do so also. That, or pay subaru to upgrade, which is definitely worth it. Carplay is my poor man’s GPS maps, music streamer, phonebook/phone, and more. And I’m poor.