I don't fully understand the logic to place hubs in locations with historically bad weather. Denver might not be the prime example, but it certainly gets its share of blizzards and snowstorms in the winter as well as storms and even tornadoes in the summer. Chicago operations lost a lot of money this year due to weather.
Why not put hubs exclusively in places like Phoenix where weather is hunky dory 350 days of the year?
Geography. Also, American and Southwest had no problem raking in huge profits in this past winter with hubs in Chicago, Delta in MSP and DTW, etc.