The space between campsites costs money for installation/ setup.
Just think of it this way.
Every extra 5 feet between campsites means an extra 5 feet of sewer line has to be laid and plumbed, and extra 5 feet of water line is needed, and extra 5 feet of electrical cable has to be added. Do that for 40 sites, and it runs into some real money.
If you are laying out an RV park, not a destination park, you are going to minimize your costs as much as reasonable, and you will want as many spaces as zoning or physical layout will allow to maximize income.
As mentioned several times, government run parks tend to provide more space between campsites.
However, I've noticed that new or newly redone government campgrounds tend to be putting in more spaces closer together.
Another problem I've seen occurred last year when we went to a COE campground where my family spend a lot of weekends in the 1960s.
There used to be 16 campsites in one area where we liked to camp, a bit close together, but plenty of room for everyone to enjoy. We were all in tents then.
Today there are 10 campsites with 45 ft long RV pads, 50A/W. The sites are incredibly crowded, about 10 ft between rigs. The slides barely leave room to walk between the rigs, or the rig and the road.
The size of the campsite we want has gotten larger over the years.
Google Earth is my friend. I always try to look at campgrounds on a satellite view before we go there. At least when I get crowded in, I'm usually not surprised.