Abuse of power! plan and simple. The Watchtower printing corporation spends a lot of effort indoctrinating people about 5 or so hours a week, and so that much indoctrination/brainwashing to Obey Listens and be Blessed gives them tremendous power over the people indoctrinated. They will even shun their own flesh and blood children if the WT so to do so.
Threat of being disfellowshipped for not believing anymore also acts as a very strong force to keep people brainwashed and never think outside the WT box,, thus firmly implanting unquestioning loyalty to their printing/propaganda business.