Cocos,
Tire covers are to protect the tire from sun damage. Tires on your car wear out before the sun has its chance to wear them out sidewall first. so no need for the car. But your RV may not get the miles on it throughout the years but the sun damage will wear at the same pace . Thus covering them may extend the life of the rubber by keeping the solar rays away. Look at some of the SUV type of vehicles rolling around. The ones with the spare tire mounted on the back of the unit exposed to sunlight. Some of the manufacturers have sold the vehicle with a tire cover on them. Not only do they look better covered but they extend the life of that spare tire.