Here's the thing: the host doesn't get any of the guest's money until 24 hours after the booking begins (basically after the guest's ability to cancel during the first 24 hours has passed).

The host's payment from Airbnb does not include fees and taxes that guests need to pay that Airbnb keeps (and passes on when required) and it doesn't include the fees and taxes that hosts need to pay that Airbnb keeps (and passes on when required). So completely refunding guests full payment can mean a host is deep out of pocket.