Why do women have boob jobs

[Mickey O leary]

I met some girls with perfectly shaped breasts, not too small, not overly big but still they were not happy with them.
I told one they were just perfect but still went ahead with the op. Her friends have big breasts.
Is the reason they choose to get them done to get the attention of men or is it to beat their friends sizes, Its a bit like houses then, if your friends has a nice big house, you go one better and build a Mansion