The Binyan Ariel writes that the verse mentions again that the Jews did not take the spoils to demonstrate that the reason they did not do so is because they interpreted Mordechai’s explicit allowance to take spoils (Esther 8:11) using the word lavoz (“to take spoils”) as an implied prohibition to do just that. After all, the word can also be translated as “disgusting,” as in an earlier verse (Esther 3:6). The Jews read Mordechai’s decree critically and in great detail, and looked at the spoils as something reprehensible, as he had implied.