I worked with some college students from South Korea, and they were very surprised that hardly anyone smokes on campus, mainly people from outside the country. Although it's decreased in the US, I wonder if the cig companies have coped by pivoting into the global market and pushing hard that way.

Also, I'm betting that alcohol consumption isn't down overall in teens, they're just smart and would never say they've had a drink or drink at any point. Speaking from very recent personal experience.