The Eruv Tavshillin works by beginning to prepare for Shabbat before Yom Tov starts. If you don't plan on eating the food on Shabbat, then you didn't really start your preparations using the designated food.
Eruvei Chatzerot and Techumin use the food to mark the collective residence of the enclosed area or to mark one's "primary" dwelling place for the Shabbat respectively. Even if you don't plan on eating the designated foods that Shabbat, they can still accomplish those goals.
That said, the Rama notes (OC 394:2) that in places where the Eruv Chatzerot is eaten and replaced each week, it should be used for the Lechem Mishneh on Shabbat, a place of honor for the object which was used to perform a Mitzva.