Because all of the scientific evidence points t his none existence. Stories in the bible ( which are literally true according to Christians ) cannot be possibly true.
Also:
God killed more people than Hitler.
It's ok for your daughter to be raped instead of angels.
It's ok to stone adulters to death
It's ok to stone homosexuals to death
You can't wear mixed fibres in your clothing
It's perfectly fine to mutilate you baby Son's genitals - I mean if this doesn't ring alarm bells I don't know what will.
It's ok to have slaves.
The list goes on and on, I really don't understand why people who claim t be spread love and peace follow a god who is hell-bent on murder and bloodshed.