the crowd of people who attempt to emulate a normal encyclopedia, with all the paper-bound encyclopedia limitations, is just too large.
The whole point of wikipedia is that it has no storage space issues and has contributors from every possible walk of life with every possible interest. People who exclude based on some arbitrary set of rules are really missing the point. After all, what possible negative effect could a small article on an esoteric subject have? Nobody reads it? So what? What if somebody does. Then the world is a better place for the article being there.