Nobody is saying anything about cheaper and easier to buy regarding legal drugs either, the price can be the same, the stigma of seeking treatment can be reduced drastically, education and prevention via delaying the age of first use (ideally to the age of majority, but it will not be perfect). AS far as killing themselves - not so much - drug related deaths will plummet since the chances of overdose would be substantially diminished.
For example, I do think it would be a more effective policy if drugs were legal.. ALL OF THEM. First off it actually does allow us to control these substances rather than ceding control to a criminal element. In my opinion highly addictive drugs (such as heroin) should be distributed only by trained and experienced drug counselors. They can build rapport with those that are addicted, they can give them hope, offer a pathway to a way out of their addiction - something that absolutely does not exist currently. The users will be inclined to go for a legally distributed product because it will be a known purity. The black market will shrivel because demand would plummet for street drugs. and the risks versus reward balance of smuggling would not be nearly as enticing anymore.
The second prong is delaying the age of first use. legality has to be aimed at minimizing the black market as much as possible (it will never go away, look at alcohol, there still is a black market, but it is very small in scope compared to what it as during prohibition). With the black market a mere shadow of its former self, we will be able to take step to keep these substances out of the hands of minors and delay the average age of first of these drugs. This in turn will substantially lower the chances of someone becoming an addict, and also substantially reduce the number of those who become users in the first place. Couple this with non propagandized sensible drug education for children and we have a recipe for reduction of usage rates over time with this policy.
The entire argument for drug legalization boils down to two words at its base: harm reduction