I follow the same logic you do, even though I disagree with what you are saying.

Lifestyle choices increase the risk of these diseases but if they caused the disease, everyone who ate the diet would get the disease, and we know that is not true.

The difference is crucial because we know genetics plays a role as well so matching diet and genetics would be useful.

Perhaps I'm mis-stating something then, because I agree with you. (Just clarified my post in case that was the issue.)