In the Hagada, the 4 sons ask questions (except, of course, for the son who doesn't know how to ask…), and they get answers. In most cases, both the questions and the answers are put in the form of verses from the Torah.
However, for the wise son and the evil son, the answer given in the Hagada isn't the answer given in the Torah for that question. (The naïve son's question and answer match, and of course the son who doesn't know how to ask doesn't have a question...)
The Wise son's question is taken from Dvarim 6:20:
כִּי-יִשְׁאָלְךָ בִנְךָ מָחָר, לֵאמֹר: מָה הָעֵדֹת, וְהַחֻקִּים וְהַמִּשְׁפָּטִים, אֲשֶׁר צִוָּה יְהוָה אֱלֹהֵינוּ, אֶתְכֶם.
and the answer given there is (translation of this - and the rest of the citations - is mine. Please feel free to edit if something isn't correct):
וְאָמַרְתָּ לְבִנְךָ, עֲבָדִים הָיִינוּ לְפַרְעֹה בְּמִצְרָיִם; וַיֹּצִיאֵנוּ יְהוָה מִמִּצְרַיִם, בְּיָד חֲזָקָה. וַיִּתֵּן יְהוָה אוֹתֹת וּמֹפְתִים גְּדֹלִים וְרָעִים בְּמִצְרַיִם, בְּפַרְעֹה וּבְכָל-בֵּיתוֹ--לְעֵינֵינוּ.
וְאוֹתָנוּ, הוֹצִיא מִשָּׁם--לְמַעַן, הָבִיא אֹתָנוּ, לָתֶת לָנוּ אֶת-הָאָרֶץ, אֲשֶׁר נִשְׁבַּע לַאֲבֹתֵינוּ.
וַיְצַוֵּנוּ יְהוָה, לַעֲשׂוֹת אֶת-כָּל-הַחֻקִּים הָאֵלֶּה, לְיִרְאָה, אֶת-יְהוָה אֱלֹהֵינוּ--לְטוֹב לָנוּ כָּל-הַיָּמִים, לְחַיֹּתֵנוּ כְּהַיּוֹם הַזֶּה
You should tell your son that we were slaves in Egypt, and G-d took us out using force and miracles, and He took us out of there in order to bring us to the Promised Land in order to follow all these rules and be G-d fearing, and that will be good for us.
However the answer given in the Hagada is
"אין מפטירין אחר הפסח אפיקומן" – we're not allowed to eat anything after the Pesah sacrifice except for a Matza that's called Afikoman
The Evil son's question is taken from Shmot 12:26,
וְהָיָה כִּי-יֹאמְרוּ אֲלֵיכֶם בְּנֵיכֶם מָה הָעֲבֹדָה הַזֹּאת לָכֶם.
and the answer that's given there is
וַאֲמַרְתֶּם זֶבַח-פֶּסַח הוּא לַיהוָה אֲשֶׁר פָּסַח עַל-בָּתֵּי בְנֵי-יִשְׂרָאֵל בְּמִצְרַיִם בְּנָגְפּוֹ אֶת-מִצְרַיִם וְאֶת-בָּתֵּינוּ הִצִּיל וַיִּקֹּד הָעָם וַיִּשְׁתַּחֲווּ
Tell him that this is a Pesah sacrifice for G-d because he skipped the Israeli's houses in Egypt when he hurt the Egyptian's
As opposed to the answer given in the Hagada which is from Shmot 13:8:
" בַּעֲבוּר זֶה, עָשָׂה יְהוָה לִי, בְּצֵאתִי, מִמִּצְרָיִם" – For this, G-d did for me when I left Egypt
So my question is: why doesn't the Hagada use the answer connected to the question, and instead provides an answer that either isn't written in the Torah, or is written somewhere else in the Torah?