With all the "stuff" in a rear bumper now (sensors, etc) I always leave the ball mount in the receiver (or I use a "Bully Step" in the receiver).
Eons ago one fall, riding with my Mom in her monstrous old station wagon with a hitch, we were stopped at an intersections when she yelled hang on - we're going to get hit!!! A smaller sedan was sliding on wet fallen leaves and piled into the back of the wagon - it destroyed his motor/radiator/heaven only knows what else. My Mom's wagon had a tiny scratch on the rear bumper. But along with that protection comes the knowledge that sooner or later your shin is going to kiss that thing....