...when the tire repair kit isn't sufficient to air up a flat, and the repair fluid gets stuck in the tube, causing 80psi to build in said tube, before it eventually unjams and sprays it all over your freshly detailed wheels and jeans, leaving you waiting for a tow in the rain.
Father recently picked up a set. Got a couple of the pinch weld pucks to prevent damage, too. Gotta say, sure makes things a hell of a lot easier. Sure, there's a bit more setup time, but good lord if it isn't worth it.