JWs are taught that there is no life outside the organization. Even though they leave, that belief carries with them. As JWs they could not interact with people who were not JWs, therefore their social skills are stunted. Being RAW (Raised As Witnesses) they have a neat little social group created for them. They may physically leave the KH, but mentally, emotionally and socially they do not know how to be without it. If they never experience what it is like to be accepted into another group, they feel lost. They may or may not believe JWs have the "truth" but, that is not important to them. People who were not RAW...are attracted to the JWs because they offer instant (although conditional) acceptance. A lonely person walks in and is immediately given a peer group. If they leave...and never find acceptance again, it's highly probably they will return.