Why haven't any Governments banned cigarette sales when it has been proven that it's harmful?
A government can try to ban anything, but in case of tobacco there are various reasons not to.
- There are people who insist on their right to smoke. They might tolerate state-imposed health-advise, but being entirely prohibited from smoking might cause them to no longer vote for the politicians who supported the ban.
- There are economical interests. Forbidding companies from selling them would mean that those people who work in cigarette production, distribution and sales would lose their jobs.
- Many countries impose an additional tax on tobacco products which generates quite a lot of tax income. Banning smoking would cause this income to disappear, which would mandate cuts on government spendings or a higher deficit. Yes, this is indeed a paradoxical situation. On the one hand, the state introduced the tax to discourage people from consuming a specific product, but on the other hand, the existence of the tax motivates the government to encourage people to consume more of it.
- As the US alcohol prohibition in the 20s or the current world-wide drug prohibition proves, banning any kind of intoxicant does not work very well in practice. It leads to a hard to control black market which requires significant government resources to suppress. Black trade with illegal luxury goods is also a catalyst for organized crime-syndicates to form which then tend to commit various other crimes.
For these reasons, most governments refrain from outright banning smoking, and rather use a long-term strategy of gradually undermining social acceptance. Making the society aware of the risks through advertising is one part of the strategy. Gradually imposing more and more bans on smoking in public places is another, because seeing less people smoke in public makes smoking appear less like an integral part of our culture.
- It doesn't seem like a state-enforced ban when everyone in your surrounding tells you not to smoke. You might not enjoy being a social outcast, but you are unlikely to make the government directly responsible when they still theoretically allow you to smoke as much as you want.
- Companies have time to react on the gradual decline in tobacco sales and move to other markets.
- The government also has time to adapt to the gradual decline in tobacco tax revenue.
- It might actually work and not just turn the legal tobacco consumption into illegal tobacco consumption of the same volume which then needs to be suppressed by law enforcement personnel which needs to be hired for this purpose.
While I generally agree with your answer, I do not believe your point 4 is a really valid reason mainly for two reasons: alcohol is easy enough to produce at home (you can literally make it out of poo), but tobacco doesn't grow everywhere - it would have to be smuggled. But tobacco would be a pain to smuggle - low value per weight and even worse value per volume. So I believe prohibition would work pretty well in significantly reducing smoking and not lead to any notable crime-related issues. Your other points still remain though.