There are two reasons why you have to get a loaner vehicle: Either you're far away from your own car, or something's happened to said car and it's in the shop. Chances are, if something's happened to your car, you aren't in good shape, either. Thus, an ouch loaner is in order.
Recently, I smacked into another vehicle quite hard. Official diagnosis: a stretched-out tendon in my right wrist, a combination of neck and back injuries that fit under the all-encompassing term "whiplash" and a very mild sprain in my right ankle.