As a starting point I think you will agree that someone who has a BAC of zero ought to be able to drive.
The majority of drunk driving accidents are the result of people that are plowed. More disturbing by far those who ARE caught and jailed have driven hundreds of thousands of miles drunk as a skunk before actually getting taken off the road.
As BAC decreases accident rates decline towards normalcy at around 0.06 its difficult to distinguish the accident rate of those who have consumed and those who have not.
People at that point neither walk nor drive funny and are very unlikely to be discovered unless you stop and test everyone or you happen to be black or Hispanic.
Instead of tightening already reasonable standards to ridiculous levels we would save vastly more lives by actually enforcing the laws we have effectively.