Is it the region's spatial isolation (Denver is not in or a short drive/train ride away from any of the five major business centers in the U.S.: New York, Washington D.C., Chicago, Los Angeles or San Francisco/San Jose)?
Is the fact that the Denver/Colorado economic development authorities are not funded to deploy massive tax subsidies to attract high profile corporate headquarters?
Is it because the Denver Tech Center, Englewood, Greenwood Village, etc are such attractive locations that they drain energy from the Denver CBD?
Its probably some combination of all of the above plus other reasons I have not identified.
Whatever the reasons, there most certainly are negative economic and aesthetic repercussions for the city and the region. A lack of HQs likely reduces regional economic vibrancy and makes locally-based philanthropic activity more challenging. The lack of marque corporate headquarters has also contributed to a dearth of newly constructed high profile, signature office towers in Denver since the 1980s real estate bust. The most beautiful office towers tend to designed by and for specific corporate owners and not as speculative investments - think Lever House, the Seagram Building, the GM Building and the Chrysler Building in New York City to take a few examples.
The factors that influence headquarters siting decisions are a running theme in this blog which I plan to keep exploring in future posts.
(photo above from Wikepedia Entry on the Wells Fargo Center in Denver).