Rewatching Sex and the City with my wife over the weekend, I queried twitter as to whether Carrie Bradshaw was the last non-villainous character to be a regular smoker on TV. A rather irate Sonny Bunch counters with Roger Sterling, Don Draper, Rust Cohle, Skyler White, Lafayette from True Blood, and Laurie from The Leftovers.
I haven't seen the Leftovers, but mostly I think these exceptions serve to sharpen the point.
Sterling and Draper are, obviously, being set in the past. Cohle isn't a villain, but he is a dissolute alcoholic. Lafayette is a drug dealer. Most of all, Skyler White the suburban mom most certainly is not a regular smoker. The smoker is Skyler White the morally-complicit-but-also-semi-captive wife of a major drug baron.
Bunch is correct that villainous versus non-villainous isn't quite the right demarcation line here. But it's that in recent shows, depicting a character as a smoker is a way of signaling that something is wrong. The difference with Carrie is that she's just a normal person who happens to be a pretty heavy smoker. Just like I was until about 2007 and like many people continue to be today. Part of this is simply because television portrayals of smoking have become much more rare. But clearly beyond that there's been an effort to really define smoking as either something that happened in the past or something that's socially deviant.