I think the audience that the framework targets is much more developer oriented, so while toolkits like jQuery have official repositories and community sites, mootools doesn’t really need these things (though in the interest of attracting a larger audience they might).

One also has to keep in mind the only framework that seems to actively advertise itself is jQuery (and from what I’ve ready they make a habit of omitting certain details).

Now, though, these frameworks have graduated from being interesting to being almost essential. It takes a while to learn one, and after you choose one, it permeates all your client-side code. So the safety of a framework’s future is now as important in the comparison as its quality. Prototype and somehow jQuery have managed to give the impression of that safety, but MooTools hasn’t. Even if it does have a safe future, the impression matters more than the reality.

I try to read up on other frameworks to compare them with MooTools, but everytime I do it I end up looking at a feature of the other frameworks, and then think “Nah I’m good with MooTools”.