Is a Cover Really Necessary?

Yesterday, I went to a storage lot in Phoenix Arizona to help a friend put some household goods in storage. This storage lot not only has storage buildings, but they also have a huge lot where hundreds of RVs are stored in the blazing Arizona sun. They have every imaginable type of RV stored here. There was not one unit with a cover over it. I mentioned this to the storage facility manager and he told me that several people have attempted to use them over the years, but they all get tired of the hassle of dealing with them. He said he frequently sees the covers in the facility's dumpster.