The dual angle camera gives you a view outward and downward for a more complete picture of what is behind you. Cameras are high resolution and low lux, so you can see the image in relatively low light.
Because backup cameras can prevent liabilities, they pay for themselves with the prevention of each accident. In some places, backup cameras are even becoming mandated by law.
See the examples below. I in the first picture there is a view of the curb, but as we look upwards in the second view there is a fire hydrant that could cause significant property and vehicular damage.