I'm told reason is there is a significant delay in transmission between BBC Digital and BBC FM, so would be annoying to keep jumping to what you were listening to 5 seconds ago.
Local stations broadcast both signals together, so are more likely to be sync'd.
My personal thoughts on the DAB are positive, I can't get KISS100 where I live on FM, but just about pick it up on DAB. Like with any regional stations when you put obstructions between you and the broadcast antenna you will get signal loss. It is more annoying on digital as you get complete signal breakdown as opposed to 'static' but can still hear the signal faintly on an analogue broadcast.
Maybe my expectations were brought down by reports of crap DAB, but I haven't experienced signal loss once when listening to Radio 1 DAB, so I'm a happy customer......so far
