I asked my husband what he thought about the excitement surrounding finding out the sex (for those who actually want to know). He gave me a long list of practical reasons that finding out can be helpful, like knowing what you need to buy (though I'm pretty sure most babies have similar needs whether boy or girl). He said that knowing helps narrow down the naming process. In our case and with all families with other children at home, knowing if a "brother" or a "sister" is on the way can be helpful in preparing the other children for the adjustment. I agreed with him but still did not feel like we were getting to the core of the matter -- the real reason that second trimester ultrasound is met with so much anticipation by so many parents.
Then, as if Katie-from-four-years ago suddenly inhabited my soul, I found my answer. Finding out that my first baby was going to be my first daughter changed the entire pregnancy experience for me. My mind immediately switched from a state of disconnect to one of intimacy with my unborn little girl. I was able to form a face in my mind, to imagine a voice that would one day greet me when I got home from work. References to "It," "My baby," and "The kid" quickly changed to "Emilia Grace." Knowing just one defining thing about my child made me feel happier at the prospect of becoming a mother for the first time.
This time is a little different. I have three rambunctious children running around to remind me what I have coming and the awesome responsibility of being a parent. The very smell of baby powder and the waterworks start because I cannot wait to powder his/her little butt. I wrote this baby a letter on a train ride just minutes after learning of his/her existence in which, among other things, I apologized in advance for all of the bossy people in our family that he/she will have to contend with. Though the bonding experience has happened more quickly this time and my pregnancy euphoria has set in nice and early, I still feel that I cannot yet see my child's face in my mind. I am guessing this will change after I know the sex of my baby. I will be able to start thinking of the baby in more personal terms, and yes, buy the right things and tell my kids whether they will be welcoming a brother or sister in May.
So I do not think that finding out the sex of a baby is a pink or blue thing for most people, at least not at the core. It is about forming those first images in our minds about our children -- images that will later be more fully understood with time.