…I was hit from behind in 2012 with six weeks in the hospital, three months off work, and five months off the bike…
The route was so calm that I was not closely monitoring my rearward view. In fact, though perhaps I could have ditched the bike, I’m glad I didn’t see it coming if I was going to get hit anyways.
I once read a comment that one should practice doing "bunny hops" so at least you could jump a curb if present on your right.
Obviously that’s the ultimate use of a mirror, and now I monitor rearwards more frequently. So hopefully being aware of the situation behind, even when not in immediate danger, allows the rider to avoid a dangerous situation, even by pulling off the road.
And other than my accident, I’ve never had the need to bail out.
IMO, besides routine monitoring rearwards with the mirror, a most important use is to make quick decisions when encountering an obstacle in front of you, such as a car door, pothole, car entering your path, etc. Can you immediately veer left?...
Personally, I use an eyeglass mounted Take-a-Look mirror that allows me to maintain a forward-looking head position with just a sideward glance to see the rear.
I really don’t want to turn my head for an over shoulder glance away from the line of travel when speeding downhill on a pothole-strewn road with heavy traffic to my left and parked cars to my right. Furthermore, wind noise can sometimes obscure the sound of a passing car.
I find mirrors so easy to use, and so helpful that I wear
both right and left.