I don't think it's purile at all. If you got drunk and accidentally killed someone whilst messing around with your shotgun on your farm, how is that different to getting drunk and getting behind the wheel of a car? Neither were deliberate acts per se, but the sentencing would be viewed completely differently. Or even remove drink from the equation if you like; an accidental killing, no matter what's used, a car, a gun or a knife, the sentences don't simply reflect that you've killed another human being.
I would go so far as to say that if a person drinks and drives, the risk of that driver then causing harm or death to another person is so high that it can't ever be ruled as 'accidental' or 'unexpected'. The act of drinking and then driving can be broken down into many deliberate and completely avoidable acts and therefore can't ever be down to pure bad luck.