[wolverine876]

I find that focusing on the mirror, aligning it in a useful way, dealing with other issues (vibrations, etc.), and then interpreting what I see in a small mirror (which might need to be realigned to see what I need) - it all takes too long. I'm much better off just turning my head - it's faster and I have better situational awareness while I'm doing it.

Bicycle mirrors aren't comparable to automobile mirrors: Car mirrors are stable in alignment - your body is in a relatively fixed position in the driver seat and so are the mirrors relative to you and the car. On a bicycle, your handlebars are moving frequently as is your head. The whole bicycle vibrates far more than a car, sometimes making the mirrors unusable. Cars have space for more and bigger mirrors.

(Also, isn't it risky attaching anything to your helmet? In an accident, as far as I know, it can both change the helmet's performance properties and also get jammed into your head.)