Because they have more fans. And those fans beat up the other teams fans, So the other team feels bad for its fans and purposely looses.
I feel like I get put on Hotshots way more often, and also that Icemen lose more often, including the times I'm on Icemen. I'm pretty sure this is just coincidence, and somewhere in the world, there's someone who gets put on Icemen most of the time, and sees Hotshots lose most matches. The maps are symmetrical, I believe.