I am assuming that you are also using sarcasm or perhaps just being deliberately obtuse . Either way, indeed it is your time and money - Just as it the time and money that your GM spent to put on that game/event . However, unlike you, that GM is being judged on the total number of actual players. It doesn't matter if you return the ticket or not ,if it is not handed to the GM it doesn't exist (in the eyes of Gen Con anyway ). Those no-shows have a direct effect of the GM's ability to put on games/events the following year(s).
Just as a theoretical exercise : What would your reaction be if you got a ticket to an event and when/if you showed up the GM/EO said "sorry ,I gave your seat to a walk-up player I knew would be here " ?
Plus if enough people feel like you do, and don't show up (just because), it hurts those who DID, if not enough are there for the event to run..