why cant carplay show me more apps while i am parked

I feel like more apps should be available to me in carplay while my car is not in motion. Why can't I watch Netflix, for example, or any other streaming app, or browse my gmail, or shop on amazon, on the screen in my car while it is not in motion? Carplay would be so much more useful to me if I could use my car screen for any app while I'm waiting in my car. I also want to be able to set my own background. Is it up to Apple, or the app authors, which apps can be used in carplay?

Eagerly awaiting carplay enhancements.