Apple Music app interrupts all other apps playing sound

Why does Apple Music app stop what is currently playing and start playing music from the Music App? For example, when I am watching TV using the Roku private listening via the Roku App, after sometime, the TV picture will pause, TV sound will stop and music from the Music app will start playing. I will then have to open the Music app, because it is not open just starts playing in the background, press the pause button to stop playback, then close Music app and press the play button for the TV to start the TV again. I have had to repeat this process up to three times while watching a movie. I have noticed it will do this in the car as well. I will have the phone paired with the car audio and be listening to a Facebook stream, and it will stop playback of the Facebook stream and start playing audio from the Music app. How to I keep Apple's Music App from interrupting other apps while these other apps are playing sound. It is very frustrating and annoying. It is almost as if Apple's Music app is jealous and does not want any other app playing any type of music or sound.