You know, it's not so long ago that it was completely normal for 13 year olds to get married. It still happens today, too, though maybe not so often in our society.
And like the above comments said, some people just have to grow up fast, and sometimes they're thrown into the adult world against their own will. When I was thirteen, hells yeah I would've loved to play with my Bratz dolls and be an innocent little joy to the world but not everybody gets to stay that innocent.
But you do make a good point about how the society is basically sexualizing kids. Media. Blargh.