“Smoking cigarettes is down to about 19% of people”
You’ll find that % increased for more than you realize if you count the “closet smokers” who because of the social implications now will not do so in public. They prefer now to smoke without being hassled by former smokers.
Additionally you are wrong to assume most want to quit....many enjoy smoking and for that reason choose not to quit.
I doubt that there are many people afraid to be known to a researcher or pollster as a smoker, or that many smokers are so indifferent to smoking or smoke so little that they succeed hiding it or want to hide it.
We know that people are interested in quitting because they admit it, and common sense supports the research, it is a rare smoker that wouldn't quit if there was a magic pill.
We all know why most smokers don't/can't quit, it is one reason that we see it as a weakness.