The Talmud (Megillah 13a) says that Achashverosh made a party, and yet Esther did not reveal her identity. He then relaxed the taxes, and Esther did not reveal her identity. He finally gave her gifts, and she still did not reveal her identity. The Me’am Loez and the Malbim point out that these were meant to work psychologically. The first tactic was meant to show how loving he was. The second trick as to emphasize her generosity. The third tactic was meant to show, through his generosity to all the nations, how much more-so he would reward generously whichever nation from which Esther hails.