The mishna (Pesachim 119b) says that one may not eat anything after the last portion of Korban Pesach. The opinion of the gemara that we accept is that after the final eating of matza, which we call afikoman, it is also forbidden to eat. The gemara implies that the reason is to keep the taste of matza in our mouths. This is strange for a few reasons, as we will now explore.

The mitzva to eat matza is a fleeting one, fulfilled when the matza is swallowed (see Turei Even to Rosh Hashana 29a). Having the taste in one’s mouth does not make it continue any longer. As a matter of fact, the taste of matza is not even a fleeting mitzva. The gemara (Pesachim 115b) says that one who swallows matza whole fulfills his mitzva, whereas one who swallows maror does not. The difference, explains the gemara, is that one requires the taste of maror but not the taste of matza. So how could the taste of matza be such a big thing?

Truth to be told, there are Rishonim who give explanations that do not focus on the taste itself. The Rosh says that the matter of the taste is just a remembrance of the Korban Pesach, which was eaten at the end of the meal. (Of course, one can ask why that is important.) The Ramban says that eating the Korban Pesach at the end makes it less likely that someone will be hungry enough to come to break bones while eating. The Ba’al Hamaor says that the taste in the mouth would remind people to say Hallel.

However, there may be a philosophical/educational reason to want to have the taste linger on. While we "make a big deal" about the story of y’tzi’at Mitzrayim (the Exodus from Egypt) just once a year, we cumulatively make a big deal about it all year long. We must mention y’tzi’at Mitzrayim twice a day during tefilla. We mention it during davening. It is mentioned in the scrolls in our tefillin. It seems always to be mentioned. Even in Kiddush on Shabbat, we say zecher liy’tzi’at Mitzrayim. One of the interesting questions that commentaries and poskim (including the Minchat Chinuch) discuss is how the mitzva on Pesach night is special in this regard. The basic answer is that there is a qualitatively more profound discussion of y’tzi’at Mitzrayim on Pesach than the mention on other days. One suggestion is that the surrounding of the story with "artifacts" of the Exodus, such as the Korban Pesach and matza, gives it added prominence.

The end of the seder, then, is a transitional period. We leave the intense study of y’tzi’at Mitzrayim behind and move on to the time where it will again just be mentioned. Perhaps the taste that lingers is a message. Take some of the intensity and the depth of the seder experience and have it linger on as long as it can. Realize that the reason that we mention y’tzi’at Mitzrayim all year is because it is such a formative event. Realize that if it were practical, we would discuss it in depth all the time. Realize that there is a time when we will move on but we can and we should allow the "taste" to impact our consciousness and our subconscious.