Marketplace network effects – Hosts are more likely to use Airbnb because they have the most guests. Guests are more likely to use Airbnb because they have the most hosts.

Instant book – A host can only have "instant book" on for one platform at a time, otherwise their listing could get overbooked. They'll likely leave this on for Airbnb because they have more guests than any other platform, which adds friction to booking for other platforms.