Good question. I use my real name here, because I enjoy the notoriety. However I do appreciate some of the clever handles that some use on other boards. Example: "The ill-tempered clavier."
To answer your question, some hubbers are concerned about their professional reputations. For example, it would be impolitic for some research scientists, using their real names, to express strong beliefs in UFO aliens on hubpages. Nobody wants to be the laughingstock of his profession.