I believe it’s because most Christians aren’t really Christians, they are Christianists. They put on an outer appearance of piety, like we put on costumes for Halloween. But they wear these costumes all the time. They like the social benefits that come with pretending to be pious. They have lived their lives listening to people in a position of authority and believing everything they were told. Even when they are told bullshit, they put energy into believing it. To them, faith means believing what they’re told. Even if they’re told to send money for a piece of the true cross, or for a little vial of holy water. Christianity is not a religion anymore. It’s a social group.