black market
Taxation also causes this.
Most studies found that raising cigarette prices through increased taxes is a highly effective measure for reducing smoking among youth, young adults, and persons of low socioeconomic status. However, there is a striking lack of evidence about the impact of increasing cigarette prices on smoking behavior in heavy/long-term smokers...
https://www.mdpi.com/1660-4601/8/11/4118
Ideally multiple methods would be used together, but claiming taxing it more is the only good solution is a stance that lacks nuance.