Why did Chazal not enact that Chanukah should be celebrated with joyous feasting like they did with Purim? (First explanation)
Many answers have already been given to this question, but we can give another answer based on the rule that it is forbidden to benefit from the Torah, because the Torah was given only in order to rectify the soul and not for the benefit of the body.
For this reason the Torah does not write that the reason for the festival of Shavuos is to celebrate the giving of the Torah, but instead wrote that it is to celebrate our bringing of “a new meal offering to Hashem” (Bamidbar 28:26). Because if the reason for making the festival was because of the giving of the Torah it would look like we are benefiting from the Torah since we are gaining a festive day because of it, and therefore this cannot be the reason for making the festival. Instead it is because of the bringing of a new offering, and thus the celebration is for the earthly benefit that we gain by meriting the bringing of a new offering.
Similarly, the festival of Succos is described in the Torah as “the festival of ingathering at the end of the year, when you gather in your produce from the field” (Shemos 23:16), so that the main rejoicing of the festival is because of the earthly benefit derived from the ingathering of the year’s produce, and not because of the spiritual benefit that we derive from the fulfillment of the mitzvos of Succah and the four species. And similarly with the mitzvah of Bris Milah the main rejoicing is because the father merited to be given a son, who was circumcised on the eighth day.
Therefore, since on Purim it was our lives which were saved, it was appropriate for Chazal to establish a festival which is celebrated with feasting, to celebrate the bodily benefit that we received on that occasion. But on Chanukah it was our souls which were saved, and since the Torah was given only for the benefit of the soul and not for the benefit of the body, if we would celebrate the occasion with feasting it would seem as if the Torah was given for the benefit of the body. Therefore, Chanukah was established to be celebrated only with thanksgiving and praise, rejoicing that the soul benefits from.
Why did Chazal not decree that Chanukah should be celebrated with joyous feasting like they did for Purim? (Second explanation)
An additional reason is because when our enemies make a decree whose purpose is to coerce us to change our religion, the law is that even if the decree is to wear a certain color of shoelace one should give up one’s life rather than follow the decree. Thus, since the decrees of the Greeks was for this purpose, many Jews gave up their lives in order to sanctify the name of Hashem, and many endured much affliction and suffering.
Therefore, if when the decree was annulled Yisrael rejoiced with feasting it would seem that their main rejoicing was because they no longer have to suffer and no longer have to give up their lives for the sanctification of Hashem’s name. Thus it would appear as if giving up one’s life for the sanctification of Hashem’s name is a bad thing, and therefore they rejoiced when they were saved from this.
But the truth is that it is a very good thing, and the reward for one who publicly sanctifies Hashem’s name is so great that if a person would realize how great is the reward that he receives for this he would constantly wish for the opportunity to sanctify Hashem’s name, even though it may entail much suffering. Therefore, it is certainly inappropriate to rejoice when such opportunities cease because of the annulment of the decrees.
However, although the reward for one who publicly gives up his life to sanctify Hashem’s name is very great, the soul does not benefit from this, because it much more prefers to continue living in order to do more mitzvos and good deeds than die and receive a great reward. As Chazal teach in Pirkei Avos 4:17 “One hour of repentance and good deeds in this world is better than all the life of the world to come”. Thus, although the lowly body desires the great reward, the soul desires doing mitzvos and good deeds than all the reward of the world to come.
Therefore, whilst the decrees of the Greeks were in force and people gave up their lives for the sanctification of Hashem’s name, it was good for the body since it received a great reward for its suffering, but bad for the soul since it could no longer continue doing mitzvos. Thus the soul benefited from the annulment of the decrees because it could continue to do more mitzvos and good deeds, and so Chazal enacted that the festival of Chanukah should be celebrated with thanksgiving and praise which gladdens the soul but not the body.
But if they had enacted that we should celebrate it with joyous feasting it might have seemed that our main rejoicing is the rejoicing of the body because they no longer needed to give up their lives, and this would have implied that giving up one’s life for the sanctification of Hashem’s name is bad, G-d forbid, and worse still people might have mistakenly concluded not to give up their lives any longer. Therefore they established that Chanukah should be celebrated only with rejoicing for the soul and not for the body in order to impart the message that the body did not benefit from the annulment of the decrees because it is good to give up one’s life for the sanctification of Hashem’s name.
But on Purim there was no decree to convert to another religion or be killed, and thus no opportunity to sanctify Hashem’s name. It was simply a decree of annihilation. Therefore when our lives were saved from this evil decree our bodies definitely benefited, and therefore Chazal established that the occasion should be celebrated with joyous feasting to gladden the body.