I use it to inspect video frames by frames, particularly being able to go back one frame. VLC doesn't support it, this thread about the feature is hilarious https://forum.videolan.org/viewtopic.php?t=120627
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> It can be added in theory, but there would be certain problems. Like said earlier codec frame access is very problematic (I, P and B frames), because in worst case scenario you have to decode about 248 sequential Full HD H.264 frames before you can get previous image (so there will be major LAG).
Having used the 'previous frame' feature in mpv, I suspect this is exactly how it's implemented.