Chromecast works differently. Casting something causes the receiving device to load a web app that then plays whatever you were playing. Yes, that tiny thing actually runs a cut-down version of Chrome OS. In other words, it's not merely an audio/video streaming protocol. Your phone/computer acts as a remote, and it's the Chromecast itself that does the streaming.

That's only for apps that support doing that, though, like Netflix, YouTube, Spotify, Twitch, etc. If you're casting a game or something that's local content, then it will obviously still stream it directly.

AirPlay does this for some apps as well.

Aside from specialty DoD-type phones, iPhones (and Apple devices in general) are the most locked down devices on the market. You can't even install an open source app without going through hoops. On Android you download the APK and click the "accept risk" button.

This was not about the devices, but the protocol.

Arguably, this is about just as locked down.