The Mishna 4 of the 10th Perek of Pesachim ends with "And he expounds from the passage (Sefaria):
מַתְחִיל בִּגְנוּת וּמְסַיֵּם בְּשֶׁבַח, וְדוֹרֵשׁ מֵאֲרַמִּי אוֹבֵד אָבִי, עַד שֶׁיִּגְמֹר כֹּל הַפָּרָשָׁה כֻלָּהּ
"An Aramean tried to destroy my father” (Deuteronomy 26:5) until he concludes explaining the entire section."
Seems like on a surface level, we would need to read the entire section of אֲרַמִּי אוֹבֵד אָבִי which is Parshat bikkurim, but in the Hagadah of Pesach we don't read Parshat Bikkurim entirely. Why is it?