This was pretty evident on PanAm and most set-in-the-60s shows, all because they don't want to look like they're promoting smoking.
Pan Am did show some smoking, but the reduced amount didn't bother me as much there because flight attendants weren't allowed to smoke during the actual flights even in th 60s. Mad Men has had no problem showing plenty of smoking (and other terrible 60s behavior such as the attitude of Betty toward her kids or the ridiculous littering). I understand not wanting to "promote" smoking, but especially for a gangster/cowboy show, it just makes no sense not to at least have the Bad Guys smoking. Breaking Bad, Hell on Wheels and Deadwood would have been stupid without the drinking/smoking/drugs. I just wonder what the next sanitaization of the past on network television will be.