When smokers in the study quit, their immune response got better at one level, but it didnt completely recover for years, according to the article
From what we already know about traditional tobacco marketing strategies, they tend to focus on the youth (candy cigarettes, now banned flavored cigarettes, cartoonish characters, sweet/candy-like flavors of smokeless tobacco etc.), the plethora of liquid nicotine flavors now available would seem to make it much easier to attract younger customers
Freud might say it was a reaction against Hockneys father, who loathed the habit years before medical science supported him
Some states have different tax and regulatory policies
Outbreak of Lung Injury Associated With the Use of E-Cigarette, or Vaping, Products