Tosafot (s.v. hakol) discuss the reasoning behind making “HaMotzi” on the top matzah Pesach night and making “al achilat matzah” on the broken matzah; since we do not perfom mitzvot in “packages” (ein osin mitzvot chavilot chavilot), it is inappropriate to recite both berakhot on the same matzah. The question is then raised as to the difference between that situation and Kiddush, in which the berakhah of Kiddush and of the wine are recited over the same cup.

The Netziv (in his Hagaddah, as cited in Eretz HaTzvi, 4) explains that the two situations are not comparable, because in the case of Kiddush, the berakhah over the wine is not merely there to cover the berakhah obligation applicable to all foods, but is an integral part of Kiddush itself.

This is actually a question dealt with by many achronim. It would seem that there are two ways to view the obligation to recite Kiddush over wine, in addition to the question of whether it is a biblical obligation to accompany Kiddush with wine (see Mifareish to Nazir 4a; Rosh, Pesachim 101; Ran to Shabbat 23b), or a rabbinical one (see Tosafot to Nazir and to Pesachim 106a; Resp. Rashba, I, 614; Sha’agat Aryeh, 60). On the one hand, wine may fill a role similar to the role it plays in the recitation of other berakhot, such as birkat hamazon and sheva berakhot, enhancing the berakhah experience through its presence. Alternatively, it may be, as stated above, that the role of wine is more significant, and that it, or more accurately, its berakhah, is an integral part of the Kiddush obligation.

There are many indications that the latter possibility may be true, including: a) as pointed out by Rav Soloveitchik (Shiurim L’Zekher Abba Mari, II, p. 134), the dominant position of Beit Hillel (against Beit Shammai) that the wine berakhah is recited before Kiddush; b) the question of the Talmud (Rosh HaShanah 29a; see interpretation of Ritva) as to whether this berakhah is classified as a food berakhah or a birkat ha-mitzvah (see Resp. Har Tzvi, O.C. I, 156; Resp. Avnei Ya’akov, 86; Resp. Eretz Tzvi, I, 62.); c) the comment of Rashi (Eiruvin 40b) that the wine is tasted out or respect for the berakhah, [instead of assuming that the berakhah is to permit the wine] (see Afikei Yam, II, 62; compare Resp. V’Shav V’Rapha, I, 14)

Several issues are affected by this question, including: a) the opinion of R. Chaim Brisker (see Eretz HaTzvi, and Mo’adim U’Zmanim, likutei ha’arot to III, 243) that one cannot fulfill Kiddush by listening, if one does not hear the berakhah on the wine (in contrast to havdalah, where it is possible, per Magen Avraham O.C. 296:10, citing Rashi’s Responsa); b) one who drinks the wine but forgets to recite the berakhah (see Resp. Avnei Ya’akov, 85); c) if a stolen cup of wine turns the Kiddush into a “mitzvah haba’ah b’aveirah” (see Resp. Tzur Ya’akov, 4).

Rav Soloveitchik (in Shiurim L’Zecher Abba Mari, and see also Reshimat Shiurim, Sukkah, pp. 295-297) explained the role that the berakhah on wine has as a central aspect of Kiddush. Shabbat and berakhot on food share a theme. In order to enjoy the specific benefit of eating, we are required to recognize G-d’s creation of those foods with a berakhah; and in order to enjoy the world as a whole, we are required to take out one day of every seven and commemorate G-d’s creation of the world. Thus, it is especially appropriate that the ritual that inaugurates the Shabbat should have as its introduction a berakhah of that nature.