Respectfully disagree. I think the RV parks are missing out on a potential market.
I, for one, would gladly pay a reasonable fee (no more than $10) for a quieter parking spot without the noise of traffic, shopping cart gatherers, and street sweepers. I just don't need even one of the services (not even the garbage can) so I don't want to pay $35 to $40 for them. The parks can have rules re what is allowed-generators, etc. I would also give those parks my business for the times when I DO want them.
You seem to imply there are lots of $10.00 options out there if one looks - Well, they're not obvious enough and, in many areas, non existent.
When RV park owners see RVs in the Walmart lot, they should be thinking, how can I get them to come and check out my park? Not - how can I stop Walmart from taking my business. The smart ones may decide to offer "FREE" parking outside their gates - with a free coffee in the morning while they show you the campground.
We're not at Walmart because we're cheap (RVing isn't cheap, after all).