Speaking strictly for myself... Yes.If you want the DVR visible, what do you want to see, the view behind you?
There's lots of occasions where I push my bike backwards through tight spaces (usually only a few mm to spare as the mirrors come past). Much easier to do on the bike, and would be nice to see behind for those times.
Can I cope without a dash mounted DVR? I seem to have done for the last 12 months...