> Less well-understood is why “place effects” matter so much for smoking (and mortality) for those without a college degree.

Let me take a crack at it: people with college degrees tend to be found in populous places and spaces where smoking is prohibited. Plus, social pressure; lighting up a cigarette in certain company is almost like hurling a racist insult.

Just to get through college with a cigarette habit would have been a pain in the ass. You can't be darting outside N times during lectures or exams to have a smoke. If you can even do that; a lot of colleges nowadays have even outdoor smoking bans, no? That's sort of a place effect: college graduates spend a bunch of time in certain places where smoking would have been inconvenient to the point of making some people quit.