Why do some people on Socratic answer their own question?
One possible reason that a person might ask and answer their own question is to share information within the Socratic community.
One recent example was a posting (which, or course, I can not find at the moment) of the different colors names that can be used (or are useful) in Socratic.
Another reason could be that some think that difficult / tricky questions, which will add to knowledge base, are not being asked. So they raise questions and then after waiting for sometime, when no body is answering, they themselves answer it.
Yet another circumstance is where the answer to a question is too long in itself, so part of the answer is split off as a separate question.
For example, the solution to a quartic equation may involve solving a resolvent cubic equation. If that cubic is not easy, then it makes sense to create an extra question for the cubic equation, answer it, then use the result in the solution of the quartic.