Anyone can take or use pretty much anything.. You can also choose to drink a beer at the age of 18 but have to wait until you are 21 to buy alcohol. There are laws that people have to abide by.. But people also have the right to chose to do or not to do something.
Because it is illegal for an establishment to SELL them to a minor, but there are no legalities for smoking them before 18.
Because it's the law
You can smoke in some parts of the US. You can smoke under 18 in New York Mississippi Louisianna goegia and a few other
You have to be at least 18 years or older to smoke because your body can't handle it just yet. just because someone gives you cigarettes doesn't mean that you can automatically smoke them.