Why can't smoking be like drinking? Well I'm sorry, but reality isn't up for a popular vote. Smoking a little can still kill you. It isn't a sure thing, after all some few people avoid cancer even if they do smoke a pack a day for years. But a person would have to smoke very few cigarettes to only have negligible effects.
It is not just how many cigarettes a person smokes, but for how long as well. Cancer is not something that happens because of a single mutation. There are many built in safeguards that keep cells from going rogue. But if a person is using cigarettes these defenses will be rendered inoperative in some cells and eventually one cell will became cancerous. It is not true this cannot happen by smoking just one cigarette. If a person is very unlucky his next cigarette could be the one that is one too many. It is not likely, but it is possible.
Smoking less is better, but no level of smoking is totally safe. Having only one cigarette a week will probably let a person avoid cancer, but it is not a sure thing. Heck, I could get lung cancer from just the time I spend in smoke filled environments like bars and the operations room at SF cons.
Lastly it isn’t just the cancer thing, though that is the bugaboo that seems to get people most uptight. It is also how badly it will make the smoker feel before he dies. Me, I wheeze for quite a while after having been around second hand smoke for a while. If that is anything like how a long term would feel for those last few years, not being able to breath right... I would not want to be facing that.
I'm not saying a person ought not be able to smoke at all, I figure a person should take what ever risks he wants. But is this a risk that is worth it? My own way of killing myself is with our friend white death, a.k.a. sugar. I do try to limit my intake of sugar, but I don't fool myself into thinking that the amount I eat is perfectly safe or has no effect. I am not going to tell you to quit, but please do not say things that just are not true.