When I bought my new van, the dealership tried to get me for 1k on the protection to the outside and inside of the van........ Later when I wouldn't pay the full price of what they wanted, they said "to be honest" they have all the cars protected with it regardless and are only selling the warranty....
We used to do a lot of work for Scotguard, Guardsman,
Phoenix, etc on spot cleaning, and you could tell the customers who knew how to play the system... They'd get new furniture every 2-3 years because of the warranty.... And people wonder why that furniture concession went out of business....
It's basically like
@scottw said, it's a numbers game... I believe if you educate and setup the expectations of the protector, you shouldn't have a problem selling it.... Most customers "think" that the protector won't let the stain set it and leave it with no sense of urgency to clean it up.... Those are the ones who give the protectors a bad name....