There is apparently history to some of them, where they were built by the people creating the ski runs, they'd take the trees and build shelters so that they were close to the job and could spend the nights near where they worked. I honestly think that is the minority, but, none the less, they are a cool feature unique to Colorado.
Now, having been to many tenth mountain huts, I readily admit that my perception of what these huts are was a little on the high class side. Even when you look on youtube, you see these massive tree forts, some of which are two stories, have windows, and furniture! The reality is that there are just a couple of those, and most of them are elaborate lean-too type enclosures using the ground as the floor. Even the fancy two story huts are nothing more than a cool tree fort hidden in the resorts. One thing that I have found to be true is this: Where a hut exists, there is usually great skiing around it!
My personal experience with these are limited to the ones I find in Winter Park and Mary Jane. I found a few now, one in Winter Park and two in Mary Jane. The more elaborate the hut, the deeper into the trees and cliffs you need to traverse. Sometimes the trails get pretty intense, I found myself traversing some trails looking down into the trees thinking I made a big, big mistake. Some huts are located right off of Blue and Green runs, while with others you had better be confortable skiing Double Black Diamond runs through trees, rocks and cliffs.