The origins of the Bible stem from a need to control others. The manifestations of this are clearly seen through many examples throughout history and even down to this day. The GB of JWs are certainly a clear example of this as we well know.
It's actually quite clever in a devious sort of way: Since I (the one with the need/desire to control) can't be watching you 24/7, I need to convince you that someone is. The God/Angels/Demons tri-plex of supernatural omnipresent Watchers is the solution. As a form of psychological control, it's obviously extremely effective in keeping people in line.
It's an interesting question worthy of further consideration ...