Indoor smoking bans were passed during that period. This was a time period of major pushes to outright ban smoking. That’s when I saw it actually drop off.

“Throughout the early to mid-2000s, especially between 2004 and 2007, an increasing number of states enacted a statewide smoking ban of some kind.” https://en.wikipedia.org/wiki/List_of_smoking_bans_in_the_Un...