I think you've hit the nail on the head. Smoking bans seem to have started in bigger, densely-populated cities. I think when you stick more people together, you need more rules, and some of these rules are going to be pretty burdensome.
People being what they are, I don't see any other solution, in a lot of cases.
The average population density of the counties won by Gore was four-times greater than the average population density of the counties won by Bush.