Why Do I Have 2 be called a "Bandwagon" Fan?

I can understand how you became a fan of each team. I'm called a bandwagoner where I live (Southeast Michigan) because I'm a St. Louis Cardinals, St. Louis Rams and Missouri Tigers fan. I have Missouri ties, which is why I like each team. I get harred about the Cards the most, but I can at least brag to local Tigers fans about the 2006 World Series.