Skipping is for stuff of no relevance yes, but watching a full docu or most of it at such speeds seems a bit ridiculous, like as if someone doesn't have the patience or attention to hold onto a steady paced piece of film - But hey that's just my view and there are many things about the "modern" way the new generation of people do things that simply don't make any sense, like paying to watch someone play a game over a stream as opposed to playing it yourself, but that's another topic.
There is nothing slow or boring about the HL2 docu that warrants skipping or even speeding it up for example as all of the information we gather is relevant and useful to fill in the gaps of narrative lost over the decades whilst waiting for HL3 news to drop etc.