Lived in Colorado for 4 years growing up. It's totally why I can't stand them. I mean, I was like 9, and adult broncos fans would give me crap. Very weird obsession.
It's because the Nuggets and Rockies are generally pretty awful. They liked the Avalanche a while back when they were good, too. But not sure about whether or not that's still a thing. I don't follow hockey.
At least that's how it was explained to me years ago.