I don't think anyone serious about epidemiology says stuffs like that. On the other hand, it is true many people interpret what epidemiology says as such. Sayi

I don't think anyone serious about epidemiology says stuffs like that. On the other hand, it is true many people interpret what epidemiology says as such. Saying smoking is a risk factor of cancer is very different from smoking causes cancer. As you said, you must consider alternative explanations. On the other hand, people can disagree about what alternative explanations are "extremely unlikely" and "can be dropped", that's what I meant by prior. For example, nuclear test causes cancer, is probably extremely unlikely. Smoking being a risk factor of cancer is an evidence of smoking causing cancer. Being evidence of causal relation is completely different from being sufficient to prove causal relation.