It's mostly because I feel in life there are risks involved, yes even of getting fatal diseases, in many things we do. And should we start to try to eliminate each and everyone of those risky, or even potentially risky factors and body parts,then well we may very well be on a never ending quest!
For that matter even surgeries carry hazardous possibilities, hence unless a doctor specifically tells me that I must undergo a surgery I wouldn't consider going under the knife voluntarily.
Bear in mind my reasons are not linked to anything vain and worldly though.Cos having seen my auntie,a breast cancer survivor, doing what she did,I know I will not hesitate to do the same if I had to.