It is all based on social history and economics. Cigarettes raise lots of taxes and establish a baseline for breaks in a manufacturing setting. Workers need breaks every once in a while anyway and a cigarette break is a good metered interval. Beside, it kept pensions down by keeping the proletarians from living too long. Then it starting breaking down as treatment for emphysema and lung cancer were developed in the 1960s and 1970s -- that is when the anti-smoking movement started up. it is one thing if people just died, but it costs so much to treat that an anti-smoking movement was needed has got to stop. Oh well, a lot of people don't give a crap and smoke anyway.

Now ganga on the other hand... if you left your desk for a pot break, you'd be gone for hours.