Many tickets have been printed and shipped. They cannot be refunded until they can be returned at Customer Service onsite.
That is in no way a penalty to attendees who manage their schedule early.
It is certainly a repercussion late event organizers should keep in mind when planning their schedule.
Gen Con LLC
Thanks for the replies Derek and Marian. Having organized for large scientific conferences in the past I understand the complexities and I am sympathetic. I assume you are looking into best practices that might help manage these issues more effectively at lower cost. Printed tickets are pretty old fashioned.
I am new to GenCon. I did not know how to search for, prioritize and organize my schedule, and the "guides" available online to do this are insufficient. I do not know anyone who has ever attended, so I am on my own, learning by doing, hoping that if I attend again, I'll know better what to do.
In my case I am finding out about cool events that I would like to attend, for which limited seats are available, but I cannot "trade up" because something I previously signed up for is in the way. At least I understand now why this is happening.