Those are for the guy that doesn't want to go home alone. They're also good for HOV lanes if you can get them to sit down.
On a serious note, if you had to declare what the majority of your selling items are when you first check in to sell, the grounds could possibly be arranged for: real car parts, flea market crap, tools, toy cars, etc. Then if you're selling mostly toy cars in the real car parts area, they can boot you out of the meet. It would sure make it easier on the guys looking for parts.