It's so true. I first started the Boston gameday when I realized that there were a crapload of locals. The first one had about 12 people, the second one about 5. I thought "Oh no!" Nowadays our attendance is only limited by the size of the place where we're holding it. We've averaged about 3 a year for 9 or 10 years.
They're always a blast. I think we've only had one player who was rude or inappropriate.
Different locations handle things differently. DC and NC have sweet conference or university facilities they use, and lots of people can game at once. Chicago uses the wonderful Games Plus store. We tend to hold Boston Game Days in peoples' homes, so we're more limited on how many games can run simultaneously.
Clearly, we need more Boston members with access to large facilities...