If your tenant does not pay you, you have to evict him. If your tenant does not obey park rules, the park's only recourse is through you, by evicting your home, which is complicated because your renter would have tenant's rights with respect to you that would make it difficult to evict your home without dealing with your tenant and his rights to live in what he is paying to live in.
A second reason is that rentals devalue parks on the theory that owners take better care of their homes than renters. A third reason is many lenders won't write loans in parks that allow rental of the mobile homes. If there is no loan available in a park, all homes have to sell for cash, which significantly devalues the homes and makes it hard to have all the homes occupied in the park when times are tough.
Terri's answer is good too.
Perhaps, if you own a home in a mobile home park and you are thinking of renting it out, it is time to sell it. I've sold several dozen mobile homes in Santa Clara County over the years. I'd be happy to meet with you to discuss your plans for your mobile home. You can call me at 408-639-0211l.