Not that all of this information will go into the manuscript, but it builds a fullness and richness of character and setting that the readers will feel. And, by understanding the rules of your world, you can expand the reality and believability of the entire work. If the characters don't exhibit these qualities, the characters will seem flat. Granted, not all characters are like this, but these are the ones that are worth writing about, and the ones that are fun to write about.
Card also reviews the specific protocols that sf readers bring.
Finally, he briefly reviews the market for short sf and the business of writing. Writing sf is a shaky field at best, and until you are certain that you will be earning enough to live on, don't quit your job. Card does for science fiction and fantasy what Rust Hills did for the short story as a form in Writing in General and the Short Story in Specific. Card has organized his personal musings about his craft into an in-depth analysis of the sf field. This work is valuable for anyone who writes sf.