>>385788728
It's to prevent it getting in the way, if anything it makes tangles more damaging as you're putting all the twisting tension on a smaller section of the cable. You also don't want it attached all the way down the back of your head like that otherwise it bends sharply.

If you want a cable to last you should try to avoid twists and any sharp bending. Even then I've had the outer coating of a cable wear down just from rubbing against my shoulders and back.