People have been backing up without cameras or proximity detectors for decades. I'm sure these systems may cause less accidents put I don't really see the need for it personally. Good thing for that kid you had one. 
Nobody needs these things....it's a nice to have and it's VERY convenient. When you have numbers like this:
The cone had to be a little over 18 feet to be seen from the driver's seat of a Dodge Grand Caravan minivan and it was invisible up to 25 feet from the back of a large Toyota Tundra pick-up.
From the driver's seat of a Chevrolet Suburban, a large SUV, the cone wasn't visible until it was 46 feet, nine inches away.
For a shorter driver, the blind spots are even larger.
18ft. 25ft. That's a very long distance. Every little gadget helps. The cars/trucks/SUV's nowadays are bigger and more about style over function. Smaller windows, higher beltlines....none of it helps visibility. Technology can help right some of those wrongs...
People HAVE been backing up without a camera for decades....but what's your point? People also rode horses and travelled in wooden wagons as well....society progresses.
