Just my guess, as a Denver-area resident... Metro Denver has several areas with very high concentrations of office space and jobs (Downtown, DTC, Broomfield/Interlocken, Boulder, etc.). Also, the residential density (even within Denver proper) varies a great deal. The lower-density areas probably don't have great bus service. (The residential density also seems to be increasing, with a lot of infill development projects.) It helps that the Denver area is known for having strong regional cooperation with a single transit authority, instead of the crazy mix of poorly connected services in Silicon Valley.
Silicon Valley office space seems to be a little more spread out. When I was visiting a client in Santa Clara last year, I had to walk almost two miles to get to a light rail station to go have a nice dinner in downtown Mountain View. (And there were no buses available to cover that distance -- at least not that Google Transit knew about.)
(Disclaimer: My experience with San Jose is mostly limited to the airport area, and the Silicon Valley suburbs to the north.)
Silicon Valley office space seems to be a little more spread out. When I was visiting a client in Santa Clara last year, I had to walk almost two miles to get to a light rail station to go have a nice dinner in downtown Mountain View. (And there were no buses available to cover that distance -- at least not that Google Transit knew about.)
(Disclaimer: My experience with San Jose is mostly limited to the airport area, and the Silicon Valley suburbs to the north.)