Car bra protection

I spent $400 (give or take a little) on a full front cover for the PT Cruiser. We used it on our trip to Tennessee and back. Since we tow the PT on a dolly, I wonder if it wasn't a waste of money. The car is high enough that nothing much hits it anyway. But, if something ever does bounce up there, the car is protected.
I haven't noticed any damage from rubbing. Yet.
I didn't use anything when flat towing the Jeep I had, nor do I use anything when flat towing the truck.