Plenty of people who are thin get sick. Even those who don’t smoke. There are genetic problems that we may all face. I guess we should all be refused treatment for things. We’re human with bodies that fail for God knows what reasons. I don’t like the government playing God when they are the most godless people I know.
I don’t like the government playing God either but even many private insurers regard obesity, high blood pressure, diabetes, smoking etc as falling under “pre-existing” condition rules. However much these people are contributing to the system on an individual basis, intentionally or not, their behavior is driving up rates for the entire pool.