Because drivers are setting their mirrors incorrectly. So many people set them so that they can see the side of their own car - that's incorrect! They need to

Because drivers are setting their mirrors incorrectly. So many people set them so that they can see the side of their own car - that's incorrect! They need to angle it out to the point where they cannot see the side of their car, that way traffic should seemlessly be visible from the rearview mirror to the sideview mirror to the driver or passenger window.