Witnesses Of Jehovah (1986)

Not all cults are created equal, but many have the same god. Why do religious people always believe the world is going to end? I think the reason for this has to do with how pessimistic their world view tends to be. People that are depressed to not wish for things to exist forever, and the opposite is true for those that are optimistic (Buddhists, etc believe the world/universe is eternal).