There is much discussion of the "dumbness" of those still in and the reason that they stay.
Some of the reasons that I have seen are:
They want everything in black and white.
They prefer to leave thinking to others.
They are scared to be shunned.
They are just ignorant souls who are on the "opium of the people"
They dont want others to think bad of them.
While I agree that there is no one single reason and that everyone is different, I feel that the real reason is a much deeper one.
Throughout all of history, mankind has pursued an understanding and knowledge of the future.
From scientific predictions to horoscopes and other various methods, it is almost universal that people seek to know what is coming.
The borg offers that. And it offers thorough training and critical "facts" to support their claims. And although their "facts" are full of holes, to many unaware of the subject material, no matter how "intellegent" they are, the "facts" speak for themselves.
Most of the literature from the WTS is presented in a "textbook" fashion, which impressively convinces people that the contained information must be correct.
So you end up with people who are seeking a future being given "factual" information and regular "pump ups" necessary to continue the falacious thinking which leads them to believe that they do indeed "know" their future.
Even when doubts start to protrude into their comfortable world, they are not then prepared to easily give up what "answers" humanities lifelong passion.
It does not make them stupid, ignorant nor gullible, it just means that they are human like the rest of us.
BugEye