Standalone is 100 % on the mark.

I had a friend who liked to get roaring drunk, and then bike down the hill. One night he woke up in the back of a jeep, with a torn plastic back window. He never would have crashed if he'd had his wits about him. And while he got the bruises, the people who owned the jeep weren't thrilled. The bottom line is that riding a bike when you're very drunk is a bad idea, and it puts more than just the rider at risk, so it's other peoples' business as well. And, as Standalone pointed out, it puts other people ( and their property ) at much less risk than driving a car drunk, so it should be treated much less severely by the law.