Or maybe the state parks hold more of an interest to more RV owners - they get some amenities along with a nice natural setting.
From reading here, few "weekenders" or casual RVers want to stay in RV Parks that cater to longterm residents - so your taking that space isn't affecting them.
P.S. There are many many houses out there. If you believe new construction is shoddy, then you can buy one of the many older to old homes. There is no law that requires you to buy a brand new home or even one in a development. To cross a stick and brick off your list in favor of an RV because a house built last week is poorly built is a lousy financial decision.