I can see Brad's point.
Other facilities many not have large enough parking lots, with room for the trailers being hauled. Or large enough double doors to let everything get in or out. Many churches have their largest gathering areas in the basement, with a single set of steps going up and down, so that dealers wouldn't be able to haul their stuff in and out. Or restrictive occupancy limits or only one or two sets of bathrooms. Or not enough outlets, amps or lighting in a room to handle the needs.
I see that some large churches only have two ways in and out of the parking lot, right out onto a public suburban street.
Interesting suggestion about public schools, because they may have the size and facilities. Yet, their insurance restrictions and school board regulations may prohibit commercial activity that is unrelated to public education. State laws may even prohibit it.
I have seen Masonic buildings and Halls in some large and small cities in the South, but I typically see only a small side parking lot adjacent to them. Maybe things are different in the mid- West?
I can understand why these types of details would be a nightmare to try to deal with.
Mannyrock