For me, I left because when I became aware of inept and corrupt elders and the leadership in New York failed to effectively address the matter. They wouldnt address it at all in fact.
I would probably not have left over the elders actions alone, it was seeing that no one is really concerned about what goes on, so much as they are just concerned with keeping the machine running.
That started me looking at the "machine" itself and well..........
I can only compare it to the wizard of Oz. In order to keep publishers in place, they must keep them from peeking behind the curtain like I did.
As for why they exist, people would love it if they could just hand over the big questions of life. Go to a few meetings a week, put some money in a box and bam! You are guaranteed God likes you AND all that goes with that...not the least of which is living forever someday in a better world.
On the surface, that seems a fair exchange and easier than picking your own path through life with no guaranteed outcomes.
As long as you dont scratch the veneer and see below the surface, it can still work for some.