or why we don't do that, it is a FOSS world?
Well, we (contributors) are stretched all over the place, and there is still a lot to do, but keeping wiki hidden on side will not bring more contributors either. New date according to Rupert's post on the firstname.lastname@example.org mail list is July 12th.
Wiki editing is not a big fun in the beginning, there is more then a few things to learn about to be able to play with, but on the other hand if you don't need fancy formating, then you can start almost instantly. Learn how to start article, then few formatting tips, like mark titles, and you are good to go.
Title in the MediaWiki is title quoted with equal signs, like == Title ==, add more = and title is smaller.
You also have to know wiki editor requires to write from the beginning of the line. Any (white) space on the begin will convert your writing in a preformatted text written in a fixed font, so there is no way to indent first line of paragraph without dirty tricks, not even for a single space.
Also, learn to use preview button, it will make you look good in the eyes of the wiki maintenance people that hate recent changes page filled with changes that are not actually changes, but someone that uses save button all the time.
There is of course more, but to correct typo, grammar or spelling, you have to know even lesser. Correcting typos is one of the ways to help, and if you ask me, just as important as being able to create fancy layout, because there is no layout that will make an article with typos look good.