Being a SketchUp novice, (Dave, I just bought your DVD recently and have not worked my way through it.) I was really impressed that Dave was able to create both main light shadow and fill light shadow and have them in differing degrees of density as they would be if one were using two lights. But imagine if one were using 5, or even more lights as is common in photographing furniture, how confusing it would be if you were able to see distinctive shadows of each light. Would you even see the subject or would your attention be taken up by all the shadows. That is why one shadow only is to be observed in any photographic image; there may be highlights of varying intensiveness but only only one shadow. Because you sometimes see multiple shadows it doesn't make it "more better".
All television has multiple lighted scenes (journalism would be an exception) but any showing multiple shadows is usually lighted poorly unless the other shadows belong to a different set in the same scene.