Any video streaming application worth its salt will stop downloading the video track if the user backgrounds the application, turns off the screen or otherwise makes the video surface not visible, so there's no bandwidth wasted in that particular scenario. This is of course somewhat diminished by people not actually turning the video off in many scenarios - and I'm not even sure Netflix supports backgrounded playback, for that matter.
Additionally, videos of still images compress remarkably well, to the point where the image itself is largely the same size as the video track.
Additionally, videos of still images compress remarkably well, to the point where the image itself is largely the same size as the video track.