This way team members will always watch a particular clock position based on your current facing ( that is you are always facing 12 o clock )regardless of compass direction. So for example you can have a specific team member always guarding your left and right flanks and rear regardless of the compass direction you are facing.
Compass directions do not stay the same relative to your direction of travel or facing. For example East may be 9 o clock or left but when you change movement direction by 90 degrees right the person assigned east watch is no longer watching your 9 o clock or left but is now watching your 6 o clock or rear though it is still east. So say you are clearing a building using a "file" formation you can have on member always watch your left another always watch your right etc, etc. regardless of your direction of travel.