There’s no first principles reason tobacco is a legal product. If it was invented today, as a product which kills or disables a large percentage of its users, it would be banned.
Only the combustion of the plant is the problem though - not the addictive parts of it: artificially created nicotine enjoys an open market globally. Tobacco is in a sense demonized due to the direct idea that it’s combusted — nicotine pouches are legal everywhere in the EU but the ones with tobacco are banned sans Sweden.
Nicotine pouches were first sold in year 2008 according to Wikipedia.
Tobacco is anyway in decline after it was demonstrated to kill people not directly using it. There have been efforts at limiting alcohol, some catastrophic. Practically nothing has been done yet about concentrated sugar.
It’s worth noting that tobacco consumption has decreased in many places, especially high income countries, but it’s increasing in many countries