People talk slow:

There is a certain risk that viewing a talk (even if its content is interesting) gets boring after a short period of time. The reason for that phenomenon: people talk slow. If we read a book, we usually receive much more (relevant) information per time unit than when we listen to a talk. (That's likely the reason why reading books or articles is in general more stimulating than listening to talks.) A sometimes useful "solution"/improvement: e.g. for youtube-vidoes: (A) click at settings (the gear wheel icon) (B) set speed at 1.25;

[via Emil Kirkegaard]