The decline in smoking has absolutely been accompanied and/or caused by a massive array of state coercion, from requiring all their advertising to prominently state "THIS WILL KILL YOU" to limiting who's allowed to sell it to banning it in almost all public spaces. (Which isn't even mentioning the "softer" approaches of massive state-funded PR campaigns against it.)

It seems quite likely that absent all of these, smoking would still be as popular as it ever was.

Not to mention the incredibly high taxes on cigarettes.