Thank you for the topic, as I was thinking about the same issue today.
Of course there are exceptions but in general I find videos for most scientific and technical topics just an easy/lazy way to reach more viewers and revenues as most of the time all that is shown which is mainly speech could be formulated in a written text and in times of HTML even with embedded animations/short videos when needed as sometimes such can tell more than words. Formulating a written text is of course much more time taking and tiring as its not as forgiving as free speech in front of a mic, although some might answer that editing a video is also time taking, yes, but usually not as demanding.
Reading a written text allows the reader to adapt all the time the "transfer speed" according to his needs and previous knowledge, something which is not as nicely possible in a video. Unfortunately watching videos is very popular to the current youth so I understand if people do it trying to reach it, although it is a vicious circle in the end. Sorry, but I am tired and just cant stand anymore the usual 20-60 minutes videos of one or few guys behind a mic where in the end I have the feeling that the topic related entropy isn't more than of a couple of A4 pages which I would have read in a fraction of the time. I am afraid its in many cases also addictive vanity, since being in the (social) media is a life target that gets stronger and stranger, giving the illusion everyone can be TV/movie/radio star.
Disclaimer: Above is not specifically related to ASRs video but the general WWW trend to spend more time and effort for videos than for classic written communication.