That's due to fire regulations, there has to be a certain distance inbetween tents, and fire breaks every 20metres or so.
Every festival has to do this these days, so as soon as you've set up your tent, you have to move your car to the car park.
If your an exhibitor, then your car is on show anyway, but if you're just a normal punter at a car show, you'll want to show it off a bit, and at least park it where people will see it, not in a car park 2miles away.