I have to ask but why is it so differen from showing horses, dogs, cats, rabbits, rats etc?
I think showing cavies is very different from horses, dogs, and cats because cavies are prey animals. (I addressed this a bit in my post above). And like Cavies-and-Kids said, cavies are very sensitive to changes in their environment. Most become quite stressed when in strange places.
As for rabbits and rats, also being prey animals, most of them behave in a way similar to cavies. They don't enjoy strange places or strange people.
Cats, dogs, and horses tend to enjoy shows more. They enjoy doing agility, and meeting new people and other animals.
The problem with all shows of course is the emphasis on breeding to achieve the "perfect" pig/cat/dog/etc. This only contributes to the pet overpopulation problem.
Personally, I have no problem with pet expos, local shelter-organized shows, friendly pet get-togethers, etc. Because in these cases the animals are mixed breeds, often from rescues, and they are loved for who they are, not compared to some unattainable breed standard.
~Eris~