In as much as Sundays are a waste for shows that size, my guess is the building is rented for the weekend and subsequently they charge vendors for that. If the show was only one day, the rent for space would still be the same.

I doubt any spectators go both days unless they missed something the first day. And of course most will go the first day because they want first crack at stuff.

The Sunday spectators are usually the few people who had to work Saturday or the "church crowd" ... looking for something to do after church so they go to the show but they don't spend money.

If they did make it a one day event, it would likely be a Sunday.

The only shows that justify being more than one day are the shows like Carlisle, where its a real challenge to do it in a day.