I worked the tight switchbacks on a shelf road at Elephant Hill near Moab with my front and rear lockers on. The switchbacks are so tight that on one switchback that the designated route is not to make the turn but simply go forward and complete the next straightaway backwards. The others are pretty tight too, but I think I had only one 2-point turn. Of course, you can turn yours off if you want to. I'm just reporting.
I think the answer to WHY is because 1) you don't always KNOW when you will need them (not all lines are intuitive. many are counter-intuitive, especially when in new-to-you terrain) and 2) sometimes you THINK they are on when they are not and 3) then you might be in trouble and not prepared for a safe recovery, and 4) yes, I have seen breakage when this occurred.