From what I've seen, many kids kind of bide their time until they're 18 (that "no-longer-a-minor" age), and once they get to 18 they, to one extent or another, get a little carried away with having passed that 18th birthday. Of course, kids who didn't give a hoot about what was legal or what their parents allowed don't always worry as much about getting to 18. I mean the ones who care, for the most part, about what their parents think and/or the law.
It was a long time ago, but when I was between mid-teens and mid-twenties it was common for many young people to smoke, say, when they were out with others who were smoking, or to have the occasional couple/few cigarettes but generally remain non-smokers the rest of the time and forever. Smoking doesn't become a habit unless someone allows it to be. Even then, though, it may not become a nicotine addiction unless it goes from easily managed (and "empty") habit/practice to something the person eventually relies on for "mood or stress reasons". That aside, I'm not sure how many people there are who found their first cigarette a pleasant experience.
In any case, considering what 18-year-olds are allowed/required to do, no, I don't think the age should be moved up. With the state-of-affairs with regard to what teens do these days; and with the state-of-affairs with regard to the numbers of people using all kinds of stuff that affects their ability to think straight, see straight, and/or operate machinery (including vehicles); I just think everyone has bigger fish to fry than worrying about who smokes at 17 versus 20 or 22.
Keep in mind that unless someone sets their house or the woods on fire through careless smoking; or, I suppose if they have a health condition that will immediately and drastically be made worse by smoking in one's teens/early twenties; health problems associated with smoking are nowhere near as immediate and/or life-ruining as some of the other things people decide to do when they're young, "young-at-mind", and/or just generally not very good at making the wisest choices.
Again, our whole culture has bigger, bigger, fish to fry than this particular issue. Besides, address the other sources of worry, horror, and stress and maybe a lot fewer people will even want/need to smoke in the first place.