It's an option for some people to run with. I run my game at an extremely low FOV which cuts off the mirrors for me (cause I prefer to have 1:1 ratio in terms of sizing, so my monitor is a window instead of just a screen)
Also, it's sometimes just easier to run. If you noticed, the mirrors are REALLY big on the left and right and it's hard to look over at them and not get disoriented. If this were with VR, i would turn it off. With triple monitor, rear view mirror is the way to go.