I am trying to understand why an Inkscape manual is not part of a public wiki. I have seen the manual that Tavmjong Bah has very kindly and painstakingly provided, but it does have its faults as well. Steps can be either confusing or problematic. Software updates cause certain steps or instructions to become invalid. A simple example (not being nit-picky, but pointing out that non-experienced computer users will try and follow the manual as well) is instructing a user to click the OK button when it is actually an Apply button.

These types of fixes are those that the general public could be very helpful in providing. Because Inkscape is open source, I would think that user contributions to a wiki-style manual would be fantastic.

Is there a reason that this is not so?

I think you can email Tavmjong if you find any mistakes.

You can become a team member at FLOSS manuals and contribute there, and I thought you can register on inkscape.org and edit wiki, have you tried it?