I certainly agree that:
1. not everyone who smokes will get lung cancer; and
2. some people who don't smoke will get lung cancer.
That said, I hope you'll agree that smoking does increase the likelihood of a person getting lung cancer.
Well, I believe that many things can lead to lung cancer. What about the coal miners that develop black lung? Not all of them smoke. It's just the pits, no matter how you look at it.
Of course not everyone who smokes gets lung cancer. The primary type of DNA damage done by smoking on the genome within the lung cells is repaied by specific enzymes within the nucleus of these cells. In fact, given differential rates of expression of DNA repairing enzymes, many people probably can tolerate a lot of smoking before a cell obtains the minimum number of mutations to become cancerous.
It is also true that the studies linking smoking to health issues are observational studies that are not scientifically constructed trials. Who is going to be part of such a trial? Smokers select themselves. However, the disease rate increases are observed. If it is not the smoking then we must be selecting for some other cause that is correlated with it. Does anyone have any ideas?
I too don't like the government getting involved with the choices that I make. I hate the idea of a nanny state. I believe that restaurant owners should be able to have smoking sections. If I want to smoke then so be it.
The difficulties arrive when money becomes involved.