This is why I installed a convex mirror on each side-view mirror on my Jeep. A guy in this tiny little import car was riding right in my mirror's blind spot, combined with the sun when I looked over my shoulder, preventing me from seeing him. I almost ran him clean over. I installed those mirrors and I can now see pretty much everything. I can see cars coming up behind me in the two lanes on each side in those mirrors all the way until I can see their front windshields directly out my windows, so my blind spots are gone.
Helmets are good for bikers.
Dome mirrors are good for everyone.