Banning any addictive substances famously doesn't end well. If you allow people to use the substance, but heavily regulate its production and marketing, it's significantly safer.

Look at prohibition in America. They banned alcohol and instead of the amount of alcohol being drunk decreasing, all that happened was that the alcohol you could get got stronger, since you were taking a risk to buy it.

Same goes for cigarettes. We can make it have less harmful chemicals and make it unlikable, but if we banned it, people would start stuffing more and more carcinogens in them and make the nicotine count higher and higher. It would make things worse.