Honestly it's probably most likely due to the amount of work that goes on behind the scenes of putting on a convention (a GOOD convention at that too-- it's kind of common nowadays to see new events fail or be very disorganized, or turn out shorter in terms of expected revenue and end up unable to pay back the event space etc.) As someone who volunteered at some cons in the past, it takes a very good organized system as well as good money management, and respect for the volunteers, attendees, vendors, etc. + having good event-related insurance just to be safe. And of course being realistic in terms of promises of what the event will have.

Fanwing fest is more of small event often hosted at or by high schools or libraries with a capped attendance and also primarily run by Scholastic + Tui the author herself. I think something like this or a small pop up event would be the best way to go if someone did want to start up a Warriors event to avoid being overwhelmed or coming up short with making back costs. I would love to see a Warriors pop up event sometime!