No reason.Can you provide some examples of why this is useful? This is simply a nanny feature someone in the digital camera industry convinced some govt official to force us to have.
I used mine this morning to check my hitch carrier with a bike on it. Thursday to watch my friend 4 wheeling behind me. And to see the terrain when backing out of a tight spot. A day before that to see the plate of the guy tail gating me.
Also when lining up a hitch ball with a trailer. Or to see what that thing you just ran over is (or if you missed it).
It's just a tool to give the driver more awareness of their surroundings.
Fun Wheel Drive