A parable:

A certain smoker has noticed that s/he has been coughing a bit lately and rationalizes that it's the weather- hey, everybody's been coughing. It's the season, for pete's sake. S/he also has noticed that s/he gets winded a bit more and sooner than usual. But hey, s/he's getting older - no one expects to be able to run the distance they could when they were 20.

Besides, if s/he were to quit smoking, who says it would help anything? If there are creepy crawlies in her/his lungs already, in all likelihood it would be too late to make a difference That would mean that s/he had denied her or himself a pleasure s/he thoroughly enjoys, for no good reason.

And besides, most people who quit smoking gain weight. And if there is one thing s/he has never wanted, it is to be fat Who wants a world of fat people? Not her/him.

And besides, s/he knows people who quit smoking and instead of saving money from not buying the ciggies they buy a whole lot more food, and junk food at that.

And besides, etc, etc...