It makes perfect sense. Cigarettes are cancer death machines in an addictive package. They should be banned. However, we've learned from hard experience that making addictive drugs harder to get just leads to addicts trying even harder to get them. So what's a practical solution? Grandfather in the current addicts and try like hell to keep everyone else away from it.
Equality doesn't come in to this. You do not, in fact, need to protect people's right to addictive cancer sticks.