Every thing that is saved on this website takes up space, and accessible covens are viewable space. For a while, there were covens constantly being made. At one point we had more than 50 I believe. That was wasted space, and viewable by the public.
There is not way to tell for sure why Pet turned off that feature unless someone directly asked him and he replied. Whatever the reason, it doesn't seem the "Create a New Coven" feture will be returning anytime soon.