[photojosh]

Mainly because of bike snobbery: mirrors are seen as for dummies. [0]

I have a rearview mirror on my road/commuter bike that replaced the plug on the bar end and it works a treat.

[0] http://www.velominati.com/the-rules/#66

[chrismorgan]

I find that mirrors don’t work particularly well on bikes (I had one years ago but gave up on it), but the implementation works superbly on a trike, because the vehicle is wider, the rider’s position more conducive to using a mirror (not constantly craning your neck) and there’s actually a good place to mount it.