Why aren't there a lot of large stadiums for swimming?

I recently heard that the research I submitted to the Canadian Positive Psychology Association conference has been accepted for presentation.  The title of the presentation is "Experiencing Flow Vicariously:  Is Watching Social Flow Better Than Watching Solitary Flow?"   My results support the hypothesis that highly social sports like soccer, basketball, or hockey are more attractive to fans than swimming, cross country, or golf because of the opportunities fans have to vicariously experience flow.  In previous research my students and I have shown that, while solitary flow is enjoyable, it is not as enjoyable as social flow..  I hypothesized that this difference would also be found with people watching others who are trying to achieve flow states alone or within a group.  So, social flow appears to be a superior experience to have actually or vicariously.  And this finding may partially explain why there are many more stadiums for soccer than swimming.