It was after 'the great apostasy' of the 1980's () that the bOrg decided that it was too dangerous to have too many JWs get together. Even studying the Watchtower with anyone other than your family was not good, and certainly frowned upon.
Imagine if you became friendly with a few witnesses and started to speak your mind. Then, that could lead to critical thinking, before long that could lead to waking up to the nonsense that the WTBTS really is.