From what I can recall wine can only be used for a Shituf while bread can only be used for an Eiruv Chatzeiros. My question is: Why can't bread be used for a Shituf and conversely wine for an Eiruv?
The Gemara (71b, 81a) states clearly that an Eruv Chatzeros may only be made with bread, and a Shituf may be made with any food item (and not only wine).
Rashi (71b) explains the reasoning for this Halachah. The reason why an Eruv Chatzeros may only be made with bread is because the purpose of an Eruv is to make a single place of residence for all of the people in the Chatzer. The residence of a person is determined based on where his bread is, since that is his main staple, and not on where his wine is. The purpose of Shituf, on the other hand, is to join the Chatzeros of the Mavoy, and not the individual houses in each Chatzer. A Chatzer is not a place of residence and therefore the Shituf, which joins the Chatzeros, does not need to be made specifically with bread.