The purpose of housing is not to provide an investment vehicle nor should we optimize for this. Airbnb should just regulated out of existence in most urban markets because we are chronically low on housing and the city doesn't need short term rentals at all.
The purpose of most real estate is to provide shelter for people, not to sit empty and unused. That's exactly what AirBnb allows to those who are only willing to rent short term (because it's their vacation home and they want to be able to use it).