It appears Arab owners used to show in these working western classes a lot. In my area, you can't even find them at the shows any more. Why the decline? They seem like so much fun.
Class schedules at Arabian shows are driven by exhibitors - if people are not riding in a specific class, it is eventually eliminated from the show schedule and replaced by classes that have exhibitors.
Exhibitors can bring these classes back by requesting them and then riding in them.