AirBnB has "instant booking" for like 10% of listing but for all the rest you click "request to book" and you've instantly committed to giving the host 24 hours to respond. If they respond in the positive you're booked. In other words, once you pick one place you're on the hook for it. You can't go looking for other places just incase the host says their place is not available.
Worse, the UX has 2 buttons "Request to Book" and "Contact Host". THEY DO THE SAME THING!!!! If you click "Contact Host" it will just send a booking request. The host can charge your credit card even though you only clicked "Contact". How do I know? It just happened to me