Several reasons for this one: (I know there's another feature request to hide progress bar when paused)
1) Pausing to read subtitles, difficult when the pause bar covers up the subtitles. There has been a suggestion to move the subtitles, but I don't believe that works when subtitles are VOBSUB based.
2) Viewing details in the video on the lower portion of the screen.
3) Vanity cards.
4) There's at least 6 threads for this in the general forums, so I thought I'd add it to the request list.