I think this may be a case of language evolving/devolving and quite possibly an Americanism.

I'm British and to me backup means having a reserve or spare ready to use. You have a battery backup on your servers to step in when there is a mains problem, a photographer will have a backup camera, you backup you files regularly etc.

We would call this a reversing camera, for when you reverse your car using the Reverse gear. You can back into a parking space, or even just back up a little bit into a better spot.

One thing I'm seeing which irritates me is people are starting to call backing singers backup singers. They are not a backup the the lead singer, that would be an understudy, they are supporting like the backing on picture.