I think the difference may be because we've been hearing about the harms of smoking for decades now. So when we hear "smoking kills X people" we understand the

I think the difference may be because we've been hearing about the harms of smoking for decades now. So when we hear "smoking kills X people" we understand they don't mean that smoking is the cause of death written on the death certificate, we understand that smoking has a demonstrable causal link to a variety of reduced lung health. While most people understand that stress probably isn't good for you, we haven't had decades of ad campaigns and public health initiatives dedicated towards it. So the general public just needs time to catch up before we put stress in the same bucket as smoking, lead paint, and asbestos.