It really depends on how you booked your stay as to whether or not the park is at fault. If you booked your entire stay and weren't told at that time the park is nearly completely booked and you would have to move sites, there is absolutely no excuse. If you are taking a day or two at a time because you don't know how long you are needing to stay, that is on you and you may very well have to move often.
We try very hard to do right by all of our advanced reservations. That means keeping them in the same site. That means those who make early reservations get the best sites. That means being aware of all their special requests such as being near the bathrooms, the dog park, a pull thru etc. Often that means the last minute arrivals have very limited choices and have to fill in the vacant spots that are scattered about. We wouldn't inconvenience a guest who made their reservations months in advance to accommodate a drive up, no matter how long either was staying.