Extracting all info out of the brains would be impractical. A lot of the things humans do we do because we are humans. Our emotions only make sense because they are mechanisms of survival and passing our genes. They would be quite impractical in a singularity (although, some other emotions, specific to the digital world, may be employed). So in a sense, I can only see one force in a post-singularity utopia, driving post-humans: knowledge and understanding the beauty of it.