If you have a HGV or a bus, i understand why you would need a rearview camera. Or with an utility vehicle with high or now windows. I doubt that's what OP is driving though, i would guess he has a normal car and does not need to do heavy duty.

When i'm driving my father's utility vehicle, i can only use my side mirrors, so i'm extra careful, but with any normal car i ever drove, even large one like a Xantia, i don't see how i could have missed anybody who can move on two legs.

The only time I've used a rearview camera was on my SO "new beetle", and we both find it quite useless (i was seeing better turning my head).