Texas, Oklahoma, Missouri on Corps of Engineers lakes, someone tows the boat with the truck that will launch it, and the RV gets towed out or motored out separately. In some cases, the park might be so close that the same truck makes two trips, towing out the RV and then the boat. Not unusual for 3-4 vehicles plus RV at each campsite, in the Corps parks here.
This also works at the Oklahoma and Missouri state parks, which tend not to have entry fees and are often as roomy as the Corps parks. Texas parks complicate things a bit more with daily entry fees, which probably influences choices in Michigan and Indiana parks.