Playback controls dim the screen

Why do the playback  controls (play,pause,rewind,fast forward) cause the ENTIRE screen to go dim?

These controls should be like every other streaming platform and only show up at the bottom of the screen.

They shouldn't cause the entire screen to dim,

This is very noticeable when playing back sports games.

The user is required to move the mouse off of the screen for the playback controls (and the screen dimming) to disappear.