...What if there was a wiki that people could use to participate in the documentation, and then that documentation would become the man page with the next release? Everyone wins?

I like and use both man pages and wikis, but I'm not sure how I would even begin to participate in helping with documentation for something like a man page if I wanted to. The actual creation of the man page itself, as I understand it, is a single-user task. If you want community involvement to get source material, you're going to have to have an accessible participatory mechanism; a wiki, essentially, in whatever form that may take. But it should be easy, no?

I suppose there's also the counter argument that "people who need wikis to participate in something like git documentation are probably not the people we want writing git documentation."