I think there are 3 reasons:
First: to make tutorial one needs to know subject very well, no guessing or “hmmmm” all the time
Second: make tutorial worth making requires several hours, instead of that we can play with unreal which is more fun for us
Third: coders are either shy or autistic (borderline) so we don’t have quality microphones usually
Also about tutorial about “how to develop a game”, I have one and it is size of a quite big book.
Laters, bzr just updated.