In Birkat HaShachar we say וְהַעֲרֶב נָא יְיָ אֱלֹהֵינוּ
אֶת דִּבְרֵי תוֹרָתְךָ בְּפִינוּ -- make the words of Your torah sweet to us. And lo! When we reach this part of the torah service, where we have taken it out, read from it, savored it, and begun to return it, we can now declare that the torah Hashem gave us is in fact sweet. The Holy One blessed be He hears prayer and answers, just like we said in shomea t'filah! Before we have even completed the morning service we have proof positive of the efficacy of prayer!
The least we can do, therefore, is to serve lekach at the kiddush, as a reflection and reminder of the answer to our prayers.