This seems to be the general case for user-contributed sites. People who are fans of a subject (be it football or model trains) may consistently use such sites

This seems to be the general case for user-contributed sites. People who are fans of a subject (be it football or model trains) may consistently use such sites but generally aren't invested enough to create content or do much beyond argue briefly when they feel something is totally incorrect, generally healthy people have healthy lives and don't get intensely invested in curating an internet forum. On the other hand, people who have unhealthy lives become totally invested in that forum or space because it's literally all they have and guard it like a mother hen guards their eggs. In Wikipedia they create a huge bureaucracy which excludes all but the most determined of users. That intensity drives away all casual users. On the other hand I once made an edit to a Wikipedia page from an IP address - I removed an unsourced claim from the Ron Paul page - and didn't find my edit reverted or blocked in any way. So while I have heard of the issue of frighteningly intense editors camping pages as though their life depended on it and demanding all changes be proven to the nth degree it doesn't seem to permeate the entire site.