my take:
[Optimistically] It's because heart disease is the #1 premature cause of death while lung disease is just #3 (though the percentage gap is much wider than their positions suggest) and therefore a good target for helping society at large through regulation[1]
[Pessimistically] the #1 cause of poor health conditions is heart disease, and therefore the medicare/medicade cost is too high for the govt to foot the bill, so they're finally regulating. :P
Smoking causes more cancers than just lung cancer. Cancer is the #1 cause of premature deaths - although that's including all 200 odd sum of cancers, not all smoking related.
For a more fair comparison you would have to sum together the cancers it is linked to, then factor the number of deaths of those cancers that were smoking-related. Which makes the math a bit trickier:
Not to mention there are non-death but still health-related issues that add up medical expenses. Which is a bit harder to quantify.
Also, as mentioned prior, other people suffer because of smokers from second-hand smoke. I feel strongly about this because I grew up with asthma and almost died at age 6 from an asthma attack that developed because of my father's smoking.
Smoking can kill the people around you. Eating transfats won't (unless they're sharing your food).
[Pessimistically] the #1 cause of poor health conditions is heart disease, and therefore the medicare/medicade cost is too high for the govt to foot the bill, so they're finally regulating. :P
[1]http://thechart.blogs.cnn.com/2011/09/13/4-common-killers-in...