Paul, I agree that this is an intriguing topic, but I think it's a bit like asking a schizophrenic why they have multiple personalities - when they don't realize that they do. The best bet is to do some research on chemical reactions in the brain when religious activity is concerned. I wouldn't be surprised if there was more information there than there is here, by just asking theists why their belief system differs from yours.
My blog: The Usual Rhetoric