I think you're being disingenuous in that you're only looking at half the story. I don't use AirBnB either as a host or a guest, so I may be missing something here, but to me, this seems to fall squarely into "this is why we can't have nice things" territory.

Of course, if you have someone over for coffee, there probably is no issue. Of course, if you have many people over for a crazy party, there will probably be a boatload of issues.

The problem is there are plenty of dishonest people who'll try to skirt their responsibilities in the in-between situations. Maybe it's difficult to hide that you've had 50 people over. But if you're renting for, say, 4 people and you have 10 more people over? I'd guess it's not directly evident. So if those people aren't hell-bent on thrashing the place, but you know, shit happens? Perhaps the guest will try to say that the couch already had a wine stain, or the dishes were already chipped, or whatever. And if a neighbor complained about the noise? There were just four of us, we kept it reasonable, but we can't be completely mute.

So of course hosts will try to hedge against these behaviors. And, of course, people trying to be reasonable will get the short straw. Next thing you know, water will be found to be wet or something crazy like that.