I am retired Army and have visited a few of the campgrounds, though never stayed at one. This is our first year with a TT and may stay at some point.
The campgrounds are typically located on the Base (federal) property and some allow civilian access, such as at Ft. McCoy, Wisconsin.
Us active and retired military types usually like to use our benefits from serving our country, such as the Post Exchange or Commissary. So, staying in the campground can save us some $$, though the campgrounds prices are about the same as a local private campground.
The campgrounds are run as a Non-Appropriated Fund activity as part of the Recreation Services Department. I believe this means they are not funded by government sources.
They provide recreational equipment rentals. The equipment; from volleyball to small boats, depending on the location, may be rented by authorized personnel for limited use.
Military Units permanently assigned or on temporary assignment may rent the equipment for unit organized recreational activities for their members. Us military types like to relax too.
Also, I have observed military members on a short-term training deployment (a few weeks), bring their families to stay in their own camper at the campground.
In summary, the campgrounds are nice, though the location (proximity to attractions) and cost will probably not steer most away from a public campground.