Entries, either in person or by proxy, support the cost of the event. Too few entries and classes are closed or, even worse, the event ceases to exist.
Yesterday, I dropped off models for a display with a club member who is setting it up for me at a museum a couple hours away. I had plans (weather cancelled them) for this morning to support a cycling friend but also wanted to support the modeling friend and his event not a competition. I will be going out tomorrow to be there in person.
At any given show, some folks have to leave early and what you're seeing may be just that. A guy who enterred, stayed around through judging but had to leave before the final bell and had friends accept for him. You can't tell the circumstances.
Also, especially for the larger events, someone may have been working on a model just for that show and an emergency crops up. Why shouldn't he be allowed to pay his fee and have someone else put the model on the table. It will receive the same attention from the judges regardless of where the builder is.
And you, the paying public, get more plastic to look at, his absence makes it eassier to win the door prizes and reduces your competition for bargains in the vendor room.