Haha, it's so funny! Why did they delete this scene? In 'The Great Louse Detective', there are just few scenes of Sideshow Bob's life in the Simpsons house. They could delete the scene with singing Sideshow Bob (no comment...) and leave the scene with Bob and Maggie there. And nice picture.
Basically it's just a timing issue and they have to get rid of something. I would have liked if this was part of the completed episode, but at least the episodes can be played with deleted scenes inserted, on the DVDs.