Glass expands and contracts with temperature. Denver's 40-degree daily swings and hot-then-cold defroster habits work a chip like a hinge.
Add mountain highways where gravel gets flung at 75 mph and you get more chips per mile than most states. The fix is boring: repair chips within a few days, and don't blast the defroster on a frozen windshield with a fresh chip.
A repaired chip in Denver holds as well as anywhere. An unrepaired one rarely lasts the winter.