Your Ski is over ten years old, and I'm not calling you a Liar. Its just that you don't see the damage that cover is doing. If your gel coat was newer and you didn't wash and wax it every use, I'd bet you a hundred bucks I could walk up to your ski and show you exactly where the rubs and the chaffing is occuring.
Folks that are afraid of Road Grim or Rocks shouldn't worry, the part of the ski that takes on that abuse isn't covered anyway. (HULL) Covers are made to keep the Sun and rain off the Ski. Anyone ever put one of those old time covers called a Bra on the front of thier car. If you did tell me a lie and tell me when you took that thing off you didn't have any scratches. I put those damn things on my car because I thought it looked cooler than the dent in the grill. I laugh at that Vacuum vent bull crap they sell you when you buy most covers they say for trailering, but the real truth to that is, it gives the moisture someplace to go, so you don't get as much Mildew. UV fades the Ski prematurely, and I never understood the folks that cover anything when it sits in a closed garage either, you cover it up and people walk by it and rub up against it cuz its covered and safe, if you only would have left the cover off nobody would touch it and there again its pretty easy to blow the dust off it when its time to get it out. But hey I've only lived and learned what do I know, its just my two cents.