Why do many people refuse to believe in psychology and science, even when research has been done?

Why are many people stubborn and still doing things that it's already been proven to be detrimental or refusing things that will work in the name of religion? For instance someone can be having horrible stomach pain but due to their religious (fanatical) views, they refuse to take their pain reliever, don't believe in doctors and instead rely on praying and natural herbs... and still deal with the pain.

Or let's say someone that's young but still relies on bibles for everything instead of paying attention to scientific studies or at least give science some credit too.

Updates
5 mo
Some even make fun of psychology and science. Or when studies have already shown that yelling too much can be detrimental but someone stubborn makes fun of it, refuses to listen and still does it just because they believe nothing ever happened to them.
Why do many people refuse to believe in psychology and science, even when research has been done?
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