For one, making alcohol illegal would kill governments from federal to local as there is a long list of taxation on several levels that go along with alcohol consumption. Two is the DUI problems can be brought under control. Like most people here, I know folks that got busted for DUI. They were all coming home from some place. Not many if anybody gets drunk at home and decides to go out for a drive.
So one solution to reduce DUIs is to mark licenses. If you get busted driving while drunk your license is marked for six months. Nobody would be allowed to serve you alcohol with a marked license. Second DUI is a year with a marked license. Third DUI is a 5 year marked license and so on.
Almost all the people I know that got a DUI were coming home from a bar. These people are more addicted to the bar environment than they are the alcohol itself. If you have a marked license, you're not even allowed in the place so nobody else can buy you a drink.
Pretty simple, eh? So why don't they do it? Tax money.