«55 per cent of households have at least one DAB radio, according to Digitalradio survey by TNS Gallup», which leaves 45% not currently having access to a DAB radio. Many of the having _one_ radio has this in their home and perhaps not in their most important place: the car.
In order to elegantly implement a DAB radio in your car you need to attach a dongle to your window and run cables into a (sometimes) new radio altogether. Whilst this may be a simple procedure for _some_ it's for the vast majority a huge burden - both in terms of time and money (often costing around 3000NOK - 380USD).
It's well and fine that they started the implementation of DAB in Norway in the mid-90s, but it's just in recent times that we've seen cars come with DAB reception by default. They should at least wait until 80-90% of all cars have access to DAB before switching over - which could take I'm guessing up to 10 years.
This is like only supporting Chrome on important governmental sites - which would rightly cause an uproar on HN. Radio should be about accessibility and content, not the medium - which should change naturally and over time.