I know exactly what you are talking about. A girl I am "friends" with has a 2 y/o boy and just found out she's pregnant with a girl. You'd think she won the lottery! I guess she DID win the gender lottery 
When I started telling people I was pregnant, my neighbor who has two little girls was like "OMG, I HOPE it is a GIRL!!!". So, what if it isn't? Are you going to feel sorry for me?
Then my mom's BFF who I have known my entire life told me about 7 times that she was hoping for a girl AND said, in front of my husband, that we could only handle "one Charlie" in our family (Charlie is my stepson). Hence why the baby simply canont be a boy. Um, great. Thanks.
Thinking back on it, this is where my GD started. I didn't really feel strongly either way about boy/girl until people started making those comments and I felt like it was some kind of prize to have a girl and that people would be smug about it if I had a boy. What the hell? I mean when I think of a boy as a mini version of my husband whom I ADORE, that makes me pretty happy. But I guess a baby is good if I can't dress it up in lace and bows...