I would blame my (pretty small) commercial driving experience. But no, not really. Before I ever took a Smith System course, I would have had trouble understanding this. I'm regularly concerned, to say the least, at the complacency/obliviousness I've seen. I don't get how someone could be comfortable with not having active situational awareness of these things.
And that's the only way I can imagine it being a realistic concern that children or other drivers will suddenly and unexpectedly appear in their path. Which is the only serious kind of thing I can imagine those camera FOVs helping with. Which they shouldn't have to, because people should be cognizant that backing is one of the more risky parts of driving in terms of likelihood of any kind of collision during it, so they should be on guard -- not merely as they are backing up, but the whole way to the car. Any children in the area should be easily noticed -- unless they are lying in wait on purpose for some reason -- and positive knowledge of their locations should be actively maintained until backing is done. Nearby cars parked but still running, or with people getting in or out of them, etc., should also be fairly trivially observed and noted. If positive awareness has been broken, then so has confirmation of a clear path, and in that case it's completely reasonable to go as far as getting back out of the car and walking a few steps and taking a couple of seconds to evaluate who is within "reach" and what they could conceivably do to screw up your day in the time it takes you to get out of the parking space. It seems like it isn't that much of a reach to do some simple due diligence that should, in a ideal world, make the backup camera a solution in search of a problem.
I don't know if you're a network person or what (in 30-second hindsight, networking knowledge may not be necessary to understand the "metaphor") but often it feels as if I'm on Collision Avoidance and everyone ("everyone") else is using Collision Detection.