Well, I don't necessarily want to defend it, but I think there is a rationale to do with infrastructure. In the extreme case where everyone in a Hawaiian town offered a room to airbnb, the infrastructure would buckle under the increased population - not enough parking, some places are on cesspools that have limited capacity, water usage is a problem in some areas etc etc.

Granted there are also financial interests at stake, for example the state collecting a hefty room tax when people end up in hotels. But then that money goes to infrastructure among other things, so there is some method in the madness.

Scaling issues, in other words. All good reasons, but perhaps my cynical reasons are just as true :)