There are two problems. First, the logistics of GP's writing, and pharmacies dispensing, cigarettes for a quarter of the population. Second, when that proves unworkable, an increase in illegally sold cigarettes which provide no income for the government. A similar argument applies over illegal drugs for which there is also a demand.
However, I am not a politician. Enforcement of policies by a nanny state has its limitations. Health promotion - not threats, scare tactics, and claims which are unscientific like "603,000 deaths from passive smoking" - is the way forward.