Last time I checked, meth, cocaine, heroin, LSD, exctasy, PCP, opium, and a long list of other drugs are illegal. Same for non-prescription use of benzos, painkillers and a whole assortment of other prescription drugs. Millions and millions of people are still addicted to them as well.
Bottom line, it doesn't really matter if any substance is legal or illegal -people will find ways to abuse it. Even if you stop manufacturing it people will make it themselves. Addiction is the problem, not the substance. Using the legality of alcohol as blame is simply another excuse to drink.