Most places at recreational destinations have a minimum stay in their high season unless you can contact and go in at the last minute. They want longer stays. (Albuquerque parks place a minumum three night stay at VERY inflated prices during the balloon Fiesta because they still rent all their spots.)
It is ALWAYS easy to get a one night advance reservation along the interstates and most larger highway. People are on the move and not staying put. Only exception may be in you are there during a special event.
RVers cannot control the rules that states/commercial parks impose. You simply may need to look elsewhere for your one night stays. We can control where we spend out money................