Interesting thread. I smoked from ages 17-29. Quit 7 months before trying to get pregnant and never looked back.
Had I not quit then, I wouldn't have smoked much longer anyway, because smokers started to become ostracized (in California, at least) by the mid 1980s. Places where smoking was permitted became fewer, smaller and more remote.
Increasingly restrictive laws was partly responsible, but many bars and restaurants instituted their own rules ahead of laws. Well-publicized, large payday second-hand smoke lawsuits by employees and family members of deceased employees were big motivators for business owners to put up No Smoking signs.
Not one person (teens included) in my immediate or extended social circle smokes cigarettes or vapes. Two smoke cigars a couple of times a year, and they go outside together to do so. Needless to say, they skip the indulgence during unpleasant weather.
Smoking in one's own home has become nearly unthinkable, lighting up in someone else's will get you quickly shown to the door. Probably permanently.
Anti-smoking laws, social patterns and high prices have effectively reduced the number of US smokers. Banning tobacco (including vapes) sales to people born after a certain year would further cut the number of smokers.
Will some find their way around the laws? Of course, but the idea of a wide net is is to catch the majority of fish, not every single one. As is often true, insistence on perfection is the enemy of good enough.
I'm generally a live and let live person, but the deck is stacked against us when it comes to super-addictive tobacco, so laws must level the playing field. Same as seatbelts, motorcycle helmets and other required safety equipment laws.
Human bodies aren't designed to smoke, any more than they're meant to hurtle around at 65 mph, so we need all the protection we can get, including extending it those who don't believe they need it.