I can't think of any real downside of banning alcohol, tobacco, gambling, in terms of it's impact on "societal welfare". There is a loss of taxation, which can be put to positive ends, but as that taxation is only generated in association with such a large amount of suffering and personal destruction, it seems you would maximise "societal welfare" by at least heavily restricting access to these instruments of self-destruction, and finding other ways to raise taxation._dhj_ said:"Societal welfare" is shorthand for aggregate individual welfare. It is unlikely that "absolute" bans (or censorship) would maximise such function, but some level of restrictions (or censorship) may well be appropriate.
How does anything less than "absolute" bans on alcohol, tobacco and gambling help to maximise "societal welfare" in any way?