You have to believe though. It's like asking the people who've build their entire lives around Jesus or Muhammad to one day leave it behind. It's not so much the sunk cost, but admitting the basis of your world view is a lie is pretty difficult, if not impossible, for most people. It's difficult for people to admit they were wrong, even under overwhelming evidence.

and it does make sense. If you questioned the foundations of your beliefs constantly, you would have no stability. Religious belief systems are a social evolutionary response.