Who would be supplying the drugs?
So, the tax payer picks up the bill for this.
Well, yeah, obviously.
Your point is not lost on me, but it goes way beyond simple "legalization."
Simply legalizing drugs still means illegal importations, and rich drug dealers.
Addicts would have to be registered, and given drugs by a government's health department for your plan to work. How would a politician possibly "sell" this to the voters, given that the people taking the drugs may be on welfare, and never worked a day in their life, and the tax payer is paying for them to be high every day?