Interesting to compare this with the Audrey Fyfe case.
In Audrey's case the driver had previously killed a cyclist, then killed another after being convicted of causing death by careless driving, loses licence for 5 years and gets community service.
In this recent case, drunk driver (with a previous drunk driving conviction), in a rage, hits two people with his car (causing a bruised back and ankle in one person, and a bruised arm in another), drives off. He loses his licence for four years, and gets jailed for four months.
Now the report (in the EEN, surprise surprise) leaves a lot of speculation in the story. There's a 'hint' that he ran over the people deliberately at the start, but further reading suggests that wasn't actually alleged in court. The original charge of dangerous driving was dropped, but it mentions other charges that he plead not guilty to - there's a suggestion he was only actually convicted of the drink driving offence, but then the sheriff states, "As a consequence of your driving you injured two people, and I’ve come to the conclusion there is no alternative to a custodial sentence"
So as a consequence of injuring people a custodial sentence is necessary; as a consequence of killing someone it's not.
I should say that the Sheriff in Audrey Fyfe's case does not have a very good reputation in the courts, certainly not from my other half's time as a fiscal. Often out of order, often havving his judgements appealed, and she's surprised he's still sitting.