Walmart allows RV's to park overnight, pending available space, as they are considered some of their best customers.
If someone double parking annoys you, then an RV taking up a half dozen spaces probably bothers you too. You might also have noticed that they seem to hang out around Walmarts pretty often. Well, the plain reason for this is that Walmart likes them. According to Walmart’s website, “Walmart values RV travelers and considers them among our best customers.”
It stands to reason that this is true because having a place to park the RV that also happens to have nearly every supply you need is very convenient. So if you’re ever on an RV trip and the nearest rest stop is too far away, you know where to head.