Um, actually it has EVERYTHING to do with it.

You see, women exercise motherhood.  Pregnancy is the quintessential aspect of being a mother.  It is true that not every women can or will become pregnant.   Getting pregnant however is part of the female nature.  It is not part of the male nature.  This is because males exercise fatherhood, not motherhood.

Women cannot be priests because of what the priesthood is at it's core: Fatherhood.  You will notice that many of the debates about women's ordination are as much about what the priesthood is as who can exercise it.  It is not a coincidence that those who support women's ordination also tend to take a very Protestant notion in their theology of ministry.  The idea that ordination isn't a Sacrament but just a formal commissioning of someone specially trained in theology to represent and act on behalf of the congregation.  Indeed--if that is all the priesthood was, there is no reason women cannot get ordained.