The problem, I suspect, is that people who own their homes are much harder for Airbnb to work with than people who are renting. Airbnb grew quickly by removing friction and making it very easy for people to list space and by providing the bare minimum support to people who list places. That was "good enough" for renters because they don't own the homes and don't care as much. Homeowners might expect a level of service that would tie up a lot of resources and hurt scaling.