Sea Breeze: But I've come to realize that the reasons people leave are quite different from person to person.
I think it's because there are so many ways in which the WTS separates itself from other denominations of Christianity. Rutherford seemed to have been a contrarian, but also a man of supreme ego. Having his own brand of Christianty must have appealed to him, so he went about making changes that would differentiate it from others.
At first, that sense of separation can make someone feel unique and special. Some begin to feel differently when they have to deal with the effects of shunning, or the blood policy. Many know well the ostracism of deliberately refusing to take part in holiday or birthday celebrations. And we all know that challenging these policies risks being disfellowshipped and shunned. At some point, you will feel like something is very wrong.
A 'good' JW will suppress those feelings. Anyone else will pull back the curtain.