Although I do not own a DAB radio, the problem for many commercial radio stations is the cost of the licence (for digital transmission), versus the payback through additional listeners.
If the licence costs, far outweighs the addition advertising revenue that can be charged – then many simply cannot afford such a luxury (to be a DAB station).
Of course, no such problem exists for the BBC who are bankrolled by you and me.
Even the name has gone from the on-screen menu. Stations that ceased broadcasting in the past had their title there for weeks or months afterwards, just no broadcast.
They're still live online so it's not a nuclear attack. :)