To risk assess.
on a scale of 1-5 what is the chance of an accident (you can use fractions)
If you are looking directly ahead it has to be 5, You are going to miss all obstacles, wires, aerials etc. by not looking at up what you are doing and what is ahead.
If there was an accident what is the degree of harm 1-5.
Touch a live cable, serious injury or death therefore 5.
Multiply the two together.
You can then decide on a solution. Any number approaching twenty five (usually over twenty), you must cease all operations immediately.
At least with the mirror you are looking up all the time, and attached to the back of the head you can spin it around to view your work.
It isn't perfect. but it works.
We sell more of our mirrors to America than any other item.
I suspect they are more risk aware.