Why are there less female atheists?

[Whateverist]

We're supposed to be the more social of the two sexes.  Since religion largely relates to relationships, with God and with others, perhaps that is the trait which biases women in favor of greater participation in religion.

Also there is no arguing or confrontations!
Which is an irony in itself, since they have already devoted their lives to this being.

That was my first thought too.  Women's conversational style is supposedly collaborative.  So failing to keep faith would seem to be a greater confront for a woman.  So I agree with both of you. Of course these kinds of generalizations never apply universally.