No one wants drunk drivers on the road, but we also don't want to incarcerate people unnecessarily. We have two issues here, and technically drunk drivers are productive members of society who do not necessarily have accidents. Rather we should be concerned about those people who have had to many drinks. Yes it isn't black and white then, but so what? The law shouldn't always be black and white either.
If you pull over car A with a technically drunk person who has been driving perfectly fine, complied with every direction given to him/her, then tell them step out of the car and call a friend/family member to pick up the car, and charge them with DUI but don't arrest them. They will then be summoned to court for their hearing.
If you pull over car B with a really drunk driver who is clearly drunk, with the breatheliser only confirming what is known, then we are talking about a different issue - arrest them.