I've experienced childbirth twice now, both times knowing the gender of the baby, and if there is one thing I can say with absolute assurance, it is that there is nothing BUT surprise at the moment of birth. That, in fact, is a wild understatement. A totally brand-new human being is coming our of your vagina. It is, I venture to say, the most shocking thing you could ever possibly experience. I don't care if you're the Duggard lady, that shit is surprising no matter how many timss you do it.
So the idea that you'd be lying there, and a baby would come tearing out from between your legs and you'd be like, "Oh yeah, a complete person is evacuating my vagina. Big deal. I know its a girl already." is funny to me.
I, in fact, feel the opposite. I DON'T want to be surprised. There are too many surprises already. I want to know whatever I can. If I could find out, from the sonogram, if the baby would be into sports or chess, I'd get that info now. If I could find out where the baby is going to college, that'd be rad. I'm an in-utero information junkie.