It's due to the nature of the subject matter I think - this system was established on generic Q&A sites and SO, which either don't tie rep with moderation and rights, or, as in the case of SO, right and wrong are much more clear. With worldbuilding, it's not entirely about being
correct, while on SO, people can and tend to vote based on that. I'd imagine the future of WB will resemble that of
writers.SE more than any other site