That could very well be what I ran into at the Goodguys and Super Chevy shows, as both were held at Indianapolis Raceway Park, which is now Lucas Oil Speedway, and it is an NHRA sactioned track.
With the local shows I attend, it is the sponsoring club that calls the shots there, on top of most of the events being held on city or county park property, and one is held at the local airport.
That's probably it. I know Goodguys themselves don't have the rule, but it may be the facility. For super Chevy it may depend on the type of event.
It's probably more often a requirement of the insurance company or venue than the organizers themselves.
One local show here used to give you a "diaper" (big absorbent pad) to put under your engine to apparently save the grass of the venue. They've since stopped doing it, I assume because they realized it wasn't doing as much as they thought.
