Even the weakest disputant is made so conceited by what he calls religion, as to think himself wiser than the wisest who think differently from him.
Faced with the choice between changing one's mind and proving that there is no need to do so, almost everyone gets busy on the proof.
Once you're in charge of your job, your house, your children, getting the food on the table, doing all of this, all of the time, it'd be nice for someone else to be in charge for a bit maybe.