Because they are getting the payment. If the customer would be paying the landlord directly, AirBnB wouldn't have the responsibilty, but since the customer is p

Because they are getting the payment. If the customer would be paying the landlord directly, AirBnB wouldn't have the responsibilty, but since the customer is paying AirBnB, the buck stops there, they are fully responsible for that; the landlords aren't their employees but effectively are their subcontractors.