Believe it or not, there are illustrators out there (like myself) who attempt to control the palette of an individual piece of work. Whether for mood or tone, the color guide can be a great tool for helping you to keep your work from getting out of hand- colorwise.
If the color guide changes every time you click something in your work, it becomes useless as a tool to manage the overall color. If I click on a shadow in my illustration, I don't want to know what it's complementary colors are, I want to know where it falls in relationship to the original color palette (and key color) I chose for that piece.
As an experimentation tool, the color guide is currently great, and as such, I'm not surprised it changes every time I click something. My hope was that once I establish the palette for a particular illustration I could lock it in place. Imagine an analog painter's palette changing hue or saturation whenever they changed their brush- it would make for challenging work.
Late note:
I found out I could actually select all the colors in the color guide and save them to a new palette. Not as cool as I'd hoped as they "line wrap" based on the width of the Swatch widget and don't line up as neatly as in the color guide.