Found myself at the airport hours early for a flight. Was sitting at my gate and the flight there was going to the same airport that I was flying to. I asked the gate agent it the flight was full. He asked if I was an "elite" or whatever with their frequent flyer program. If I was not they would have to charge me a change fee. So the airline would rather fly an empty seat than fill one now and possibly be able to resell my original seat.
I opted to save the change fee and enjoy an adult beverage across the hall.