TD:
We are kept too busy to have either the time or the inclination to think for ourselves. So when the GB does the thinking for us and hands it to us on a silver platter we just accept it. We don't have time to do anything else.
Also, we are trained to not trust our own thinking or our own thoughts and motivations. If there's something we don't understand or agree with, the problem is always with US. We are too spiritually weak or too involved with the world or not studying enough....etc to be able to grasp the deeper and vastly superior understandings of the GB.
We are constantly told that doubts are a sign of sinfulness, so we push any doubts out of our mind and refuse to acknowledge them.