Fear:
At the end of day, people will reject hard scientific facts in favor of contradictory religious conclusions (evolution vs. creation, fact vs. faith, observed reality vs. imagined feelings). Why? Because people are terrified of death. If the promise of an afterlife were removed from religion, I doubt it would be nearly as popular, and I doubt that today's irritating and embarrassingly unintelligent "counter-science" movement would exist. People are willing to ignore mountains of concrete evidence (the fossil record as one example) and centuries of painstaking scientific research, in order continue to comfort themselves with the promise of eternal life that religion offers.
When you die, it's just like it was before you were born. Not so bad.
