My father was over 40 when he joined; he had just been through a painful divorce and his second wife had started "studying" a few months before him, with almost instant conviction that "it was the truth" (LOL). I have often thought that the real reason why he joined (in spite of many doubts in the beginning, and even later) was that he really hoped for a "fresh start" for his new family, with "sound moral grounds" etc. As a result he turned it into a hell.
I was only 12-13, and I guess my real motivation was a need for consistency which the WT seemed to fulfill, with an answer for every question.
I have often pondered on this difference of approach. To a 40-y-old man the "truth" could only be relative. To a teenager it was absolute. I'm not sure he ever realised the moral weight he put upon our shoulders.