United's Eastern network from DEN is quite weak for a hub of its size.
UA doesn't even serve CVG or PIT from DEN.
Before 9/11, UA's goal was to add more Eastern routes from it's DEN hub, however these plans have now been put on hold as United's main goal is to recover financially. Then when the time is right, you'll see United continue on with its plans.
There are MANY Eastern networks that United doesn't serve from DEN.
"Generosity is giving more than you can, and pride is taking less than you need." - Khalil Gibran