Why do some people say that they don't believe in heaven or hell?

The question's wording reflects the opinion that these people just "say" they don't believe in heaven or hell which implies that they actually do but don't want to admit it. In most cases these folks have done their homework, proven to their own satisfaction that these is no afterlife, god or heaven or hell. They are just being truthful.

Most people who say that they do not believe in Heaven or Hell actually do not believe that those places exist. They either (1) believe in a different afterlife from the Christian one or (2) find the evidence of a Heaven or Hell insufficient to match what they would need to believe in it.

Generally, those people are simply being honest.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.