Why do atheists use the argument that "we are born atheists"?

You don't become christians because you grow older and more intelligent through schooling. You become christians because your parents sent you to religious education and the teachers taught it to you. Since you are young and impressionable and would not ever dream that you would be lied to by an adult, you soak it up like a sponge. You never had a chance to not believe unless you were one of the few really intelligent, somewhat y kids who refused to listen to illogical ideas and continued to think for yourself.