Its manipulation and coercive control over the people in attendance, that worldly people are bad associations and any information that is not approved by the org should be avoided, because they know that jws will then question what they have been told. And discover that they have been lied too .
All religions gaslight there believers that they are the only true religion and they should believe the fantasies that they promotes as true. They don't want them to do independent research into the bible and find out that the bible is the uninspired word of man.