Perhaps it's not the right to harm ones self that's the issue. Should you have the right to manufacture, sell, and profit from harm to others? Be it environmental, oral health, lung health, or heart health, cigarettes are a net negative to any citizenry. Seems in a governments best interest to try and greatly reduce and/or eliminate this leech.
Unlike cigarettes, cannabis has medical uses and is not nearly as harmful especially if you don't smoke it (vaping or edibles). It's not completely safe (hardly any drug is) but it's on a different level of safe compared to tobacco.