That's cool that you can talk that way with your Dr. about JWs and he's able to relate somewhat.
To address why they stay, just from what your Dr. said, I think one could infer that they stay because they feel they are alone. Many who have blazed the trail away are very brave souls, and I admire them. ( I am not one of the brave ones.) Back to those stuck; if they became aware of each other, I think that would change many things. Just like survivors of a natural disater crawling out of the rubble, these stuck ones need to know about each other and support one another.
So, how do we as seasoned Apostates help these people? Its been debated here before, and I think that there is no one way to approach the problem. I do wish there was something that we could do or figure out that could reach these desperate souls seeking excape. First hurdle would be just finding them and knowing who they are.
OFC, I hope the rest of your Dr visit went well.