You can be a good driver but still make mistakes. That's why we have safety belts and airbags. I would imagine when safety belts became mandatory, people are probably saying "Oh, I am a good driver, I don't need those."
It's the other drivers I'm worried about. And a seat belt will save my life.
A backup camera? Not so much.
I personally haven't happened it to me, but my former boss backed into a kid in his truck. Didn't hit the kid hard so he wasn't even aware of it. The worst thing is, he went off the next day to the army, and he only knew about it when he came back 5 years later.
So I personally support it because situations like this. Again, cheaper than a potential medical bill or a lawsuit.
Another thing it will help is when your garage barely has enough room for your car. My RX-8 barely fits in the garage, and the sensors really help me park in that sweetspot. I know some people use sock balls, but it's not always possible to find a good spot to hang one.