Side mirrors on cars must be replaced by cameras

All cars made these days, from the Tata Nano to the Mercedes S-Class,
all have side mirrors to help the driver see behind the cars. I
propose that a passive optical system (i.e. fiber optics or lenses and
mirrors) or an active system (i.e. cameras) be used instead of these
mirrors. This would improve the coefficient of drag of the car, and
also, it would add less "appendages" to the car which has a higher
likelihood of shearing off in city parking.

Why hasn't this been done yet? It shouldn't cost more than xenon
lights.