When you have little ones, and usually it's at the same time that most of your friends do too, then it's nice to keep up with everyone and see the kids grow up. I have a "Santa's mailbox" that I keep all of the old photo cards in of all my friend's and cousin's and coworker's kids through the years. Could never bring myself to throw away any of them. Now that I think about it, I guess that is the reason for fewer cards the past few years. Once the kids become teenagers they no longer cooperate with the Christmas card photo and parents just stop sending cards altogether.
Enjoy the pre-teen years as much as you can, especially with a girl because the teen years are tough!