I don't presume to know people's motives for driving on the campground road, nor do I spend time wondering why they do. They are entitled to do so.
We almost ALWAYS do this, to check out potential sites for a future camping trip, even recording on the campground map which sites we like and might request in a future trip. We also enjoy seeing what kinds of campers people have and how they set up their sites. We don't stop and stare at them, we just slowly pass by. I never considered that anyone would be offended by our passing through. There are many far more aggregious things to get one's undies in a bundle over.