Why do others criticize people for choosing to have cosmetic surgery?

I cannot grasp this. It's the same as getting your teeth straightened. Lot of parents suggest their children do get braces. Why can't we say the same for making a few alterations for our physical appearance? Whether it be eyes, nose, chin, stomach, etc.--we have a right to make a personal choice if some of us want to nip or add a few things to our bodies. None of other people's business.