Walmart Parking coming to an end??

I have using the app that shows what Walmarts allow parking for a while now. Recently I posted that a Walmart in Mobile had changed from allowing RV's to not allowing. I got a response back from the guy that runs the app. He said that more and more managers are changing their stores to not allowing RV's. This was disappointing to me, as my wife and I travel for work in the RV and have to use Walmarts a lot during the week because most campground offices close before we get in, and don't open by the time we leave in the morning. I think that we should all write nice letters to Walmart's corporate office and thank them for allowing us to park there. We should ask them to encourage their managers to allow RV parking and point out how much we spend there on groceries and fuel. If we are forced to use campgrounds every night, we will obviously be buying our food and fuel at the closest places to the campground. It will clearly cause some drop in their business. We should point out that we don't really see what harm the RV's are causing, as we usually park in un-used parking places and are very neat. The letters would not be threatening, but mention how much we appreciate them allowing us to park there up until now. Clearly, they didn't have to allow us all this time. I think if they get enough emails/letters, they may change their minds.
Thanks