That might also be handy in the case of (say) where you are running through a security CCTV recording of a fixed view where the scene was rarely-changing, looking for any incidents, and wanted to automate the detection of a scene-change.
If you did that, you would probably need to ensure that the screenshot captured the video elapsed time counter as well, to establish at what point the screenshot occurs in the video.
Having said that, it would probably be better/faster to establish the occurrence of a scene-change by scanning the video data itself, rather than a display of the video.
Mind you, I gather that neither of the above methods are likely to be able to capture the movement of an alien life-form across the scene. We know that because no-one has so far succeeded in capturing an image of them as they move amongst us.