Here's the problem(s)...
They take a lot of time to plan out, record, edit, and post, and then by the time they're online, they're already out-of-date as newer versions of things have come out, the display or GUI changes, an operating system update makes things work differently... etc.
I have so many videos to redo it's not even funny, and that doesn't include all the new ones I haven't yet recorded. Most of my stuff is the "core" and "dirty" type video. Pioneer DJ official tends to make more of the introduction videos when a product is launched, some big-artist video demos, and some tutorial how-to videos. But look at the fact they just released the CDJ-2000NXS2 and DJM-900NXS2 videos... and how long have those products been on the market?
We certainly do encourage users to make their own videos, no harm in helping each-other! But yeah, we do what we can, when we can. ;)