One of the things European colonists brought with them to America was the love of lawn. That's why traditional landscaping in this country includes large expanses of grass. This approach is fine in the eastern United States, with its high rainfall, but in Denver's semi-arid climate many grasses need a lot of supplemental irrigation to stay lush and green. So to avoid wasting water outdoors, grass should be limited to areas that need to be useful lawn.
For instance, if you have children or pets who need a play area, then a grassy area in the back yard makes sense. If you have a sloped front yard where foot traffic is confined to the cement sidewalk, consider using with a water-wise groundcover like thyme, snow-in-summer, creeping veronica or junipers — not grass.