I can't speak for the other shows, but from doing JAX I have some thoughts on the topic. Putting on the show is of course a gigantic process and pain and each additional activity has a ripple effect in taking more of our limited time. So we kick around ideas and then pick the ones with the most bang for the buck relative to our finite amount of time. So besides issues related to getting the venue to accommodate extra hours, is the effort of getting staff, maintaining games, making sure everything is safe and secure, etc. worth it for what would most likely be a relatively small number of people, vs something else that would appeal to a larger number of people.
Still, the biggest issues are getting games to the show and volunteers. If there were more people able/willing to not only donate games but be able to bring them it would make it much more likely to even have a show, much less one that runs 24 hrs. For the last JAX I think our crew picked up and delivered close to 70+% of the games (I need to verify but that is what I remember.) Not to say we don't appreciate people donating games, only that the time and effort in moving that many games just isn't appealing or sustainable, and probably the biggest factor in why we have put off having another show.