In the first Rashi of the sixth chapter of Mesechet Brachos, Rashi writes that wine (and bread) have their own Brachas because they are important. What does Rashi base this statement off of? Where does he see their importance?
According to this article by Rabbi Shlomo Riskin, Rav Soloveitchik explained the special nature of bread as relating to the degree of human involvement required to turn G-d's creation (stalks of wheat) into edible bread.
Rav Soloveitchik explained as follows: Concerning the Seven Species, the partnership between G-d and humans is limited, with the humans performing a largely custodial task... In contrast, bread’s extraordinary journey from the field to the mouth requires a series of specific procedures. According to the Mishna’s categorization of the 39 forbidden activities on the Sabbath, eleven are devoted to the preparation of bread: “Sowing, ploughing, reaping, binding sheaves, threshing, winnowing, selecting, grinding, sifting, kneading, baking….” (B.T. Shabbat 74b)... Rav Soloveitchik suggests that the greater the degree of human input, the greater the degree of sanctity.
We may also compare the midrash (Tanchuma Tazria 5) which describes the conversation between Rabbi Akiva and Turnus Rufus, in which the human involvement of making bread is compared to circumcision. It shows how the world was created with the intent that it be completed by man.
As for wine, the same principle could apply. Grapes can be eaten right from the vine, but the human involvement of pressing and fermenting elevates the sanctity of the product.
Initially, I thought it had to do with the centrality of the 5 grains, but that would then demand that ALL grain products have a special bracha. I found this discussion of Pat akum which discusses why bread is important enough to be covered by such an edict, and in it the author writes
"The Rif (Avoda Zara 14b) and Tosafot (Avoda Zara 35b s.v. Michlal) record the Jerusalem Talmud (Avoda Zara 2:8) that states that Chazal also rescinded the Pat Akum decree because of the difficulty for most people to abide by it, as bread is "Chayei Nefesh" (one's life depends on it). We should clarify that in pre-modern times and even today in many cultures, bread is the main component of the meal (see Tehillim 104:15). Our affluent North American society in which bread does not serve such a function is an exception. Certainly, in the time of the Gemara, bread was a centerpiece of a meal (see Sukkah 27a regarding Agrippas' assistant)."
Though I have no specific source, I would assume that wine's importance is through its sacramental position or centrality to simcha.
This may come from Genesis 14:18:
וּמַלְכִּי-צֶדֶק מֶלֶךְ שָׁלֵם, הוֹצִיא לֶחֶם וָיָיִן; וְהוּא כֹהֵן, לְאֵל עֶלְיוֹן.
And Melchizedek king of Salem brought out bread and wine; now he was a priest of God Most High.