Lung cancer is still cancer, and while different types of cancers vary in many ways, they are also similar in many ways. Studies into the detection and treatment of lung cancer can (and have) contributed to the detection and treatment of other types of cancers.

From a practical perspective, setting aside issues like blame and responsibility and the dollar value of one life vs another, studying all types of disease increases our knowledge of human biology, and our knowledge of disease in general.

Keytruda is one example of a therapy that was developed to treat lung cancer (and melanoma), but now looks like it could be effective against other solid tumors that fit a genetic profile.

This is not to argue against smoking cessation (or more importantly, prevention) programs. Just that there are reasons to pursue lung cancer treatment research that go beyond the lungs entirely.