@Nita8 I have had similar, I have a strict policy, which Airbnb have changed to 50% instead of 100%, even day of. I have had a few guests like this who were 'shopping around' usually it's at peak times of the season. I added a Host Voice to suggest Guest's cancelations should be on their review page, just like cancelations are seen on hosts page even when a year in advance. It helps to know who is a serial canceler. Just as it helps guests to know which hosts are serial cancelers.
As you mention it's more than the payment, it's re-arranging one's schedule and appointments, declining dinner invitations and meeting friends to be available for the guest, preparing for the guest and incurring costs and then they cancel with no reason, not even a message to apologize. I think were it to show on their review page it may encourage more consideration.
It seems Airbnb is allowing guests who cancel, who do not even stay at a listing, to leave reviews, I assume the same for host so you can write Guest did not show up and canceled an hour after reservation was to begin.