I have been infuriated by people cutting back into the lane in front of me after they pass and realize now why they do that. They simply aren't using their rear view mirrors and are relying on false info from their side view mirrors which makes it seem like they are farther away than they really are.
As to the motor home. I keep all three cameras on all the time. I find it invaluable to know where all the traffic is around me.
I also use my side view mirrors - (former big rig drivers are we) but no single one of these tools gives us all the answers!