Yes, there are still a minority who will get wasted and get behind the wheel, and we'll never stop those people. But if we can get the majority to rethink their drinking & driving, we may save some lives/injuries.
Look, 0.00 may not be realistic in a culture like ours where drinking is the norm. But like i said in a further post, maybe a combination of more education, a cognitive function test, and personal breathalysers would help. But again, that's not going to stop the people who chose to drink drive anyway!