I find that taking that break to smoke actually increases performance.
Coding is a miracle for the smoker, and vice-versa.
When working on a specific task within my code, I refuse to go smoke, wanting to stay in the zone and get all of my thoughts in there and working - thus, savings my lungs.
After a task has been completed, especially the difficult ones, I find the 5-7 minute break before moving on to the next task to be extremely beneficial. It gives me a few minutes to unwind, gather my thoughts, and anticipate/plan what my next steps will be.
I used to smoke and found this also to be true. HOWEVER, when actually working with a team at an office I realized it was actually decreasing performance because I had to constantly dodge out back for a smoke break, completely disrupting my flow. Even most places where I've lived the past 5 years weren't really smoke friendly, so smoking just became a huge distraction rather than a concentration aid.
In addition to the obvious health and financial reasons, this was a big reason that I quit. Thus, even though I'm all for less government, I fully support smoking bans.
I wonder if the same technique would work for harder drugs. I.e. legalize cocaine and heroin, but make it so that the only place people can legally do them is in a cold alleyway 30 yards behind the pub, next to a garbage dumpster. This way you'd get rid of the drug-dealing related crime but make it seem like a pretty lame habit to pick up.