So much speculation and so little factual information. Back in the day, WalMart owned the land that their stores were built on. They set the rules about parking. Where this situation still exists, WalMart welcomes the RV traveler.
Most of the newer stores are in shopping centers where they might not even be considered the anchor tenant. The Owner/Management of the center sets the rules and has the wishes of all the other tenants to consider. The center hires the security force and WalMart holds no sway over any of them.