You cannot effectively legislate morality. Addictive personalities are inborn, and where other drugs are illegal or not available, those personalities will become alcohol or prescription drug dependent.
Distribution of illegal drugs in the country is already a multibillion dollar business with enormous profits, profits great enough to drive 80 percent of crime(by some estimates), and leave entire urban areas to be ruled by outlaws, and fund massive corruption in our legal and police enforcements agencies. We have already passed the point where drug-related crime is doing far more damage to our society than legal availability of those substances could ever achieve.
Legalize. Control. Tax. And if the use of drugs can only be called a vice, at least let the proceeds from that vice be harnessed for good.