Actually it has. Around 20% of the adult population now are smokers as opposed to around 75% in the 50s and 60s. I’d say it also has to do with the ever growing demonization of smokers. When fat begins to be demonized like smoking is, then people will be screaming, “Tax the hell out of fattening foods”.
Taxes have had an impact but I’d suggest the largest impact is the social stigma of smoking now and the knowledge about its health impact.