Sure. Go ahead. Great idea.
Retroactively, that would make Casablanca a good hard R. Not to mention that Good Night and Good Luck would become Youth Restricted Viewing at Blockbusters in SoftandMalleable, Nebraska and TieyourShoesforYou, California.
Plus, you'll only be able to find copies of Coffee and Cigarettes off this continent and people will still start smoking early anyway, here, there and everywhere.
One last plus, Demolition Man becomes a PG-13 and is slowly reconsidered to be a prophetic masterwork.
Addendum: The quote in the linked article is attributed to that guiding light of western redemption, decency, and morality, Joe Eszterhas. He also wrote Showgirls.
And finally, I know it's an evil industry. I don't dispute that. Unfortunately, we either outlaw cigarettes entirely, or we simply, at long last, quit our nagging and our overprotective whining over it. Don't want someone you know to die from cigarettes? Me neither. But we make our own beds.