Why do Jehovah's Witnesses actually go out in the Door-to-Door Ministry™?
Would they do this if they were not directed to do so by the Watchtower Society? or would they come to the conclusion to do so from reading the Bible independently?
Basically, the only reason JWs participate in the Preaching Work™ is because they are mandated to do so by the Watchtower Society, and they are ostracised if they fail to participate in the Preaching Work™. That is a form of coercion, and in such case, it isn't really something one does of their own volition, from their own understanding of the scriptures. It's something they are told to do, or else.