Because lung cancer doesn't tend to show up on xrays until the end stages. There are other diagnostic tests I would suggest you look into that would ensure that you make an informed decision.
A colleague of mine was just diagnosed with advanced lung cancer. She's a smoker, but has the small cell cancer (which is the one I think hits everyone, not just smokers). After talking with another friend who took care of her father when he just died from lung cancer (the one that smokers tend to get), I hope that people will investigate their own situations more carefully.
Thanks for the info and for caring. However, it's none of your business what I do with my life. I have survived two major cancer's in my life (neither one was caused by smoking, I might add). I will have to die from something. I doubt if I will get out of this life alive, so I may as well enjoy it!