Or maybe it's that they have competing services/apps so have no real inclination to make a 3rd party app work properly...Never used Pandora, but from what I read on other forums, Carplay and Android Auto just aren't fans of the app for some reason. Maybe it's the phone, operating system, etc.
It's not up to Google or Apple to make any 3rd party apps work properly. They've already provided the APIs sufficient for creating a usable experience, as can be seen in many other apps that use Android Auto/CarPlay properly. I'd be more inclined to think that the team that makes the Pandora app is probably just not paying a whole lot of attention to CarPlay/Android Auto.Or maybe it's that they have competing services/apps so have no real inclination to make a 3rd party app work properly...