I agree with almost all of the comments. My thought is that a person leaves when:
1. They are ready, and not a minute before.
2. They need a personal reason which is external to them such as, a Nazi in the BOE who is too demanding of them and pushes them too hard, or a CO who does the same thing-heavy handed unloving demanding pushing/watching/scruteny,etc or, when their kids have been maligned or marked inappropriately in some quasi-inquisition, or people realize that the end hasn't come and they have been waiting for decades (I know some waiting for 55-60 years) this is linked to 1914+100 years-how long do you wait? or actually how stupid are you?
3. The embarassment of the door-to-door work. Going door-to-door for decades with little result in the past 20 years or so. In the developed world the growth is practically nill. Any expansion of the religion is happening in the third world. Go back to the same neighborhoods with the latest Kingdom News Tract and tell the same householder that "the end is coming, but this time we mean it!"
4. The demonization of formal education. How can anyone be expected in the 21st Century to earn an average living in the US/Canada/Europe without a formal University Education or some specialized training in something? Forget about getting rich through an education. Just earning a living. If you live in Borneo you may be okay.
The control system used by the WTS has constructed a platform to launch people out of the religion. If its not corrected, eventually the Organization will collapse by attrition. Apostate former members have little or nothing to do with it. The main causes of disenchantment and exodus are internally created and self-inflicted.