The Florida State Pokemon League begs to differ. I think a couple of reasons for the turn out waaas.....
1. The tournament was scheduled for Sunday. Prior VGC tourneys have been run on Saturday. I can only assume most of the people are coming from out of town and driving back late on Sunday might not work out for them.
2. The tournament was announced shortly before it happened. A lot of people probably weren't prepared for this tournament.
3. The tournament was outsourced. Even though it was Nintendo backed, the websites they were linking to seemed to be kind of sketch.
4. The prizes weren't as big as they were in previous years. Now that Nats is an open invitation, playing through regionals for 300 bucks is almost redundant.
5. All of the events were run on the same day. While IMO it's not a bad thing, it doesn't work for the people that go around to all of the VGCs. There are several people that travel around to go to the VGCs(mostly during the summer where more time is available) and this effectively stops them from doing that.
6. It was run during the school year and I'm sure that deters a lot of the less dedicated players from going. During the summer when they ran the prior tourneys, a lot of people/kids are on vacation.
7. The most important reason... IT WASN'T ADVERTIZED. The only people that knew about it are in the know and keep up with it on a fairly regular basis. They don't even have direct links on the pokemon front page. They did a piss-poor job of getting the word out. Who's going to go to a tournament they don't know about. I sure wouldn't.
... just a thought, just to name a few.