I do it mostly so I don't have to repeat myself. :)

I use the clips so that others can gain from the kernals of wisdom those clips provide... without having to commit to some portion of an hour to find the kernal themselves.

Saves everyone time and enforces compliance to decisions made )

Also, of course, by manually editing down a deeply technical discussion from an hour to 20 minutes helps me REALLY listen and understand what the speaker is saying....and so it also helps me to continue improve my knowledge...