I know what you mean. For me, the Wiki is mainly useful for accessing FS information away from home- weapons statistics and cutscene scripts, for the most part. The mission walkthroughs, FRED stuff (with a handful of exceptions), ship articles are largely... how do I put this without sounding offensive...
The main reason I help maintain the Wiki is because I have nothing better to do during my "free time" at college. As Shade said, there's a lot of helpful reference; people just don't talk about it or contribute as much as they should. At the same time, there is a huge amount of... "crap?"... that is almost never read, like the half-baked FRED reference. The community could find a better use for some of that bandwith.