I think it's odd, to be honest, given the existence of the html5 video tag. Of course, last time I checked, there wasn't a standardized video codec yet, which would make it tl;dr for authors.
gifs have the advantage of working on lower-resource devices (cellphones, netbooks) without any delay.
youtube and other "feature-rich" sites work only with massive stuttering for me, so I'm happy for any gif instead of a video which needs to be set up and torn down for every play.