One reason comprised of many little reasons:
There’s a great variety of things to do. The Denver Center Theater Company consistently puts on fantastic theater productions. The Museum of Nature and Science creates and hosts fascinating exhibits. There are several art museums in town that cover a variety of niches. The Denver Art Museum is expanding to show more of their world-class collection. The sports teams work hard, have great stadiums, and are fun to root for. Occasionally you can see a rodeo. Many great musicians make sure to stop in Denver on their tours, including stops at smaller venues. There’s all sorts of places to shop, eat, and drink. Denver has all the benefits of a major metropolitan area.

Another reason:
It’s easy to get out of town. Denver is very close to the mountains, including Rocky Mountain Natl. Park, several ski areas, and an abundance of public land such as National Forests. If you enjoy outdoor activities there are an abundance of activities to choose from: hiking, biking, rock climbing, rafting, kayaking, skiing, snowboarding, camping, and nearly any other outdoor activity you can think of.

Yet another reason:
You don’t have to live in Denver. Denver has suburbs and also fairly large towns that are not suburbs but are still nearby. If you like the benefits of living near a large metropolitan area, but also don’t want the drawbacks (like urban crime), you can choose a smaller town that is nearby but still just a short drive from the big city. Fort Collins is a college town with fantastic cultural, shopping, and dining opportunities of its own (including a variety of employment opportunities as well). You could even pick a town in Wyoming such as Cheyenne or Laramie (where I live) and still be close enough to make day trips down to Denver and Fort Collins, but also have quick access to less crowded places in the mountains, a small-town atmosphere, and the energy of a college town (in Laramie’s case).

I hope this helps. I’m sorry if I sound like the local chamber of commerce, but I really love living in this area. Good luck choosing a place to move!