There is no "why" to people leaving the Watchtower Society.
You believe what they tell you to believe until you can't anymore.
Once you can't believe anymore--what else can you do but leave?
The Jehovah's Witnesses are a giant Placebo organization. It is a panacea (cure-all). You get many benefits from a placebo--but--only as long as you believe it will work.
Promises are lofty, emotional and charged with heroic storylines and cultural icons.
You join in order to plug-in to the source authority and participate in much the same way as a Renaissance Fair works.
It is play acting on a Universal stage with special dialogue, parts and activities. Role Playing can be energizing and mind stimulating if it isn't carried
to obsessive end. Of course, IT IS carried to obsessive ends.
It grows tiresome.
Stales.
JW life becomes a chore and boring, repetitious and those End Times Armageddon cure-all promises never happen.
When it is no longer heroic it quickly becomes tedious and bothersome.
You slow down, you complain, you drop out and often become outraged at the colossal waste of your time (and all that BELIEF!)
Members become testy, argumentative and rebellious.
They leave or get kicked out.
The TRUTH is a role-playing game. You really have to care about the GAME.
If you don't......if you actually GROW UP.....well, it is time to move on to more adult activities.
Why in the world would the manufacturers of a PLACEBO want to understand the product they promote is hot-air and promises?
They are honest people. They themselves believe. It would destroy their world.