> Unused bookings are pure profit for them
They want to be fully booked, because not only does it avoid the appearance and vibe of being a "ghost town", they also make a lot of money on things like the hotel bar, minibars, laundry services, etc.
If a room stays un-used, the marginal cost to the hotel does not actually decrease much, especially not in the short term.
They still pay the same to their laundry contract, they still pay the same rent, they still pay for the front of house staff and the chefs to be there, and they still pay to heat / AC most of the hotel.
They might save very marginally on some room AC not being on as much, and eventually if the reduced bookings was noticeable might negotiate a smaller laundry contract, reduce head count, but at that point you just look like a failing hotel.
I'm confident if you looked at the accounts, it's more profitable for a guest to turn up than not, even if the guest still paid for the booking.