I would guess that, the length of time a person is in the JWS, especially a born-in, would effect their fear factor. It's scary to realize that once you leave the WTS, you will be responsible for every decision in your life. Freedom = responsibility.
Once free, there are no elders, no 'mother' to tell you what is right and what is wrong. I would think that could be frightening (trying to step outside the box and think of how I would feel if I had stayed in the JWS). This fear would be deep, and the person may not even be aware of what is holding them back from accepting TTATT.
tal