The main reason for pushing DAB had nothing to do with it being superior quality, it had to do with freeing up bandwidth for other technologies. FM kind of 'swamps the airwaves'. FM uses one frequency per station, DAB uses one frequency.
Current DAB broadcast power is reduced to prevent clashes with FM. If FM were completely dropped, the quality of DAB would improve. A bit catch 22.
However I've always been a DAB sceptic. DAB radios are power-hungry, the decoders use a ton of power compared to FM, so you can't run a DAB off an AA battery for a week (unlike FM). They seem a bit redundant with improved mobile data and internet radio.
FM does use up a lot of the spectrum though. It will have to go, someday.