Sure, a drunk persons ability to make the right choice is affected. They may know it's still wrong but might just say "Fuck it" and do it anyway. That is the alcohol affecting you. Yes they would still be responsible if someone dies. But, if they make it home safe with no incident, what is the harm? They made a choice and, although not the right one, didn't cause harm to anyone.
Drunk driving is a problem for sure but a cop should just be getting that person home safe if they get caught. Imprisoning them is not the solution. Maybe making taxis and uber more available instead of banning them would help too.