We must know the sex!!! But why???

Know any pregnant people?
Even wonder we want to know the sex of our baby before they are born?
Sure, you may say that it's so they can pick a name. But why not just pick a name for both sexes and then when the baby is born pick from there? Or you may say it's better to know so that you know what kind of decor to put in their room. But why? Why do we socialize our kids like that? Why does the baby's sex matter so much even BEFORE it is born? Why do we buy pink things for someone at their baby shower if they are having a girl? What's wrong with pink for a boy or blue for a girl? And have you even looked a baby that belonged to a stranger and asked how old "he" was and had the parents snap at you, "She's a GIRL!" Well, I sure have. They all look the same to me at that age anyways. Why do people get so offended? Why have we done this in our culture? Do you see where this fits into any of Gilman's theories?