This sugya directly addresses why an eruv is unnecessary on Yom Tov: since carrying is permitted for food preparation (ochel nefesh), the Sages did not impose the rabbinic requirement of an eruv that applies on Shabbat. The principle 'ho'il' (since it is permitted for one purpose, it is permitted broadly) is invoked.
מַתְקֵיף לַהּ רַבָּה: מִמַּאי דְּבֵית שַׁמַּאי וּבֵית הִלֵּל בְּהָא פְּלִיגִי? דִּלְמָא בְּעֵרוּב וְהוֹצָאָה לְשַׁבָּת וְאֵין עֵרוּב וְהוֹצָאָה לְיוֹם טוֹב קָא מִיפַּלְגִי. מָר סָבַר: עֵרוּב הוֹצָאָה לְשַׁבָּת, וְעֵרוּב הוֹצָאָה לְיוֹם טוֹב. וּמַר סָבַר: עֵרוּב הוֹצָאָה לְשַׁבָּת, וְאֵין עֵרוּב הוֹצָאָה לְיוֹם טוֹב, כְּדִכְתִיב: ״וְלֹא תוֹצִיאוּ מַשָּׂא מִבָּתֵּיכֶם בְּיוֹם הַשַּׁבָּת״. בְּשַׁבָּת — אִין, בְּיוֹם טוֹב — לָא.
Rabba strongly objects to this reasoning: From where do you infer that Beit Shammai and Beit Hillel disagree over this issue? Perhaps they disagree about the following: The halakhot of eiruv and the prohibition against carrying out apply to Shabbat, but there are no halakhot of eiruv nor a prohibition against carrying out on a Festival. The Gemara clarifies the dispute according to this explanation: One Sage, Beit Shammai, holds that the halakhot of eiruv and the prohibition against carrying out apply to Shabbat, and similarly the halakhot of eiruv and carrying out apply to a Festival. The only difference is that, on a Festival, carrying, like other types of prohibited labor, is permitted for the sake of food preparation. And one Sage, Beit Hillel, holds that the halakhot of eiruv and the prohibition against carrying out apply to Shabbat, but there are no halakhot of eiruv nor a prohibition against carrying out on a Festival, as it is written: “Neither carry forth a burden out of your houses on the Shabbat day” (Jeremiah 17:22), from which Beit Hillel inferred: On Shabbat, yes, carrying from one domain to another is indeed prohibited; on a Festival, no, it is not prohibited. According to this explanation, Beit Shammai and Beit Hillel did not disagree about whether a prohibited labor that is permitted for the purpose of food preparation on a Festival is also permitted when it does not serve that purpose.