It leaves them looking....which is what they like.
Even if no "show" couples appear, other couples will...and a show is a show is a show, as they say....whether or not they know.
As for rules, that's a complicated issue.
Simply put, there are too many single guys looking for free sex. Many are obviously desperate, since they lock the wheels when they spot a couple parked-up.
The bad behaviour comes from wanting to be "first in the queue", I even got elbowed out of the way last week by one plank....who then had his dick out in daylight.
Like I said, desperate.
I've even heard of some guys telling others about non-existent shows and places, just to get them away. Not to mention the "you don't want to go near that one, he's got the clap" type of advice.
And we all know of the guys who spend all day driving from car park to car park on their bosses money, and getting paid as well.
Rules are only any good if all parties agree with them, but with the advantage being with the ones who couldn't give a shit about rules, and with society in general rewarding rule-breakers, the future doesn't look good.
And in any case, if the internet didn't exist I'd still be in car parks etc, only they'd have genuine doggers in them and not a load of sad planks that leave the engine running so they can make a quick get-away....with their kids toys and baby seats still in the back.