I think that makes sense too. Sure a drunk cyclist is less of a problem than a drunk motor vehicle operator.
But as the third party you still don't want 100 kg (200 pounds) of dude and aluminium frame running into you at 20 km/h (12.4 mph), especially if you are a pedestrian, a second cyclist, or a biker.
All of those sound insanely high. If you take a group of 10 random adult men from the US, roughly four of them have been arrested?
Is a lot of it for underage drinking because that law is so far from lived reality?