Part of the recurring problem for Game Days, in particular, is the ever-present affliction for gamers, in general. I speak of, of course, 'flaking.' People say they'll go, others make plans to go, then a cascading effect of "Oh, nevermind, I'm busy afterall" occurs, which then results in 2 or 3 people showing up.
If a good number of people were to make a concerted effort in showing up for game days again, I imagine we'd see them happening more often, which would have the added effect of increasing attendance because of that, and thus increased interest in others.
In short:
Less people go, less people are interested.
More people go, more people are interested.
You can't have too many people at a game day, really, thus the only detrimental effect is when people keep not going. Plus, it's free money for the chapter, which goes to improving events, props, monster camp, etc.
So, yeah. Game days are good. If people actually show.