The gemara says that R' Yehuda would abstain from wine because it made him sick, but would push himself to drink wine for kiddush, havdala and 4 cups on pesach (in my sefer i discussed how much suffering one is required to go through to fulfill a mitzvas aseh). For the 4 cups it makes sense that he had to push himself because the mitzvah was to drink and he could not be yotzei through the drinking of someone else (although tosafos pesachim 99b implies otherwise - famouse brikser rav on this issue). But kiddush and havdala he could have been yotzei from others, why did he have to push himself to drink?
A friend of mine pointed out to me that the ADERES (father in law of R' kook) has a kuntres that was just published where he writes some short hear'os on the chayei adam klal 68 (chaval i didn't have it 3 months ago!). In this kuntres called "machshirei mitzvah" he cites a sm"a (c.m. 291:27) explaining a gemara in baba metziah 42a that a talmid chacham makes his own kiddush and is not yotzei with others. Although the Magen Avrohom (296:10) wonders why this would be, the ADERES suggests that being yotzei from someone else is like a shliach, and we always say that the mitzvah is greater when one does it by himself and not through a shliach. Interestingly enough, he points out that the statement made in b"m 42a is by rava, because rava is the one who claims in kiddushin "mitzvah bo yoser m'bshlucho". The ADERES goes so far to say that it may be better to make kiddush on bread in order to do it by oneself rather than being yotzei through someone else - obviously a very big chiddush!