The strongest visual elements are the most useful ones: navigation menus and featured content, not background colors. Perhaps this occurs because of our familiarity with nature's color combinations. We are used to backdrops composed of blues, yellows, and grays because we see them every day.
This phenomenon becomes especially important in web-based applications where users can interact with an online service for hours or days at a time. Having a palette that does not fight for a user's attention allows them to focus on their work and on important information.