AirBnB already owns the touch-point with customers who are looking for non-traditional places to stay. Some portion of those customers would also be open to normal hotels, and AirBnB could serve them by doing something as simple as adding another check-box in the "home type" interface. Once word got out that you can do both things in one place, there would be little reason to go through any other service and they would take an ever-larger share of all bookings. Of course, this is won't happen, because hotel operators, seeing this danger, will refuse to integrate with them. But that huge market opportunity is still there, they "just" have to build their own hotel capacity to realize it.