Possibly because it's increasingly more expensive to produce an event, and in order to draw sufficient enough crowds to warrant one, you need to appeal to a wider audience, and also attract a a broader base of vendors willing to pay for their few square feet of space on site. It could also be that there are competing events within driving vicinity, and you might have to take what you can get. Finally, it could have something to do with rival factions vying for control and behind-the-scenes politics that sometimes happens when missions collide over scarce resources.

Those are my thoughts.

Regards,
Rex.