Walmart overnight parking

did an 8 week trip from NH to Idaho and back through many states. Quite a number of Walmarts have posted No Overnight parking. Some will allow with permission regardless. Some told me the police will likely knock on my door during the night because of local ordinance. I am on private property so whats up with that? Local Walmart policy I think. So the problems are: some lots are not owned by walmart and since 24 hour stores are a thing of the past security may toss you. people that are drug/alcohol addicted or have dissassociated from society have made old rvs and parking lots their home. If an RV is abandoned at walmart its not going to be a later model. Walmarts are having issues with getting them towed because the owners don't claim them and the tow companies don't want them taking up space. Then there are the issues of prostitution, drug dealing, dumping black water etc. Not pointing fingers at every older model but these are real issues.