I think for many of the people who remain in this group their reasons for doing so are mainly social.
The pressure to conform, the desire to be accepted and approved of by the group etc - all natural desires which WT is happy to exploit. For those people they stay for social reasons and they leave for social reasons.
When things are going fine socially they can overlook any mistake or gaps in logic presented by WT. Then, when something very painful happens or maybe a succession of painful events that causes their "faith" to shatter they start to question the things they were previously only too happy to ignore and they are no longer able to cut WT the slack it needs to keep the lies going. If someone acts on these feelings of "someting is not right here" and starts to research WT for themselves that's when true awakening can occur.
In my experience with trying to prove, convince or persuade others truth cannot be told it can only be realized. This point you alluded to in your post and for that reason if I see a JW now and cannot avoid chatting with them I talk about anything and everything but the"truth." Far more effective for them to see me happy and well adjusted.