The Torah has lots of laws and doesn’t usually specify that we have to keep them; it’s assumed. The Torah’s expectation may be a little ambitious, but its threshold requirement is no less than full observance. While this may be difficult for some people in practice, the Torah pulls no punches and makes no exceptions. So when the Haggadah highlights one particular mitzvah that we have to observe, it sticks out:
אֲפִילוּ כֻּלָּנוּ חֲכָמִים כֻּלָּנוּ נְבוֹנִים כֻּלָּנוּ זְקֵנִים כֻּלָּנוּ יוֹדְעִים אֶת הַתּוֹרָה מִצְוָה עָלֵינוּ לְסַפֵּר בִּיצִיאַת מִצְרָיִם – Even if we were all wise sages familiar with the entire Torah, the mitzvah is incumbent on each of us to discuss the story of the Exodus…
If we correctly assume that we are supposed to observe all the mitzvos, and tonight’s mitzvah is telling the story of Egypt, then what is the point of the Haggadah saying that we have to do the mitzvah – מִצְוָה עָלֵינוּ?
R’ Benjamin Blech notes that even though everyone has to keep all the mitzvos, it’s only rarely that every single individual has to do something for themselves. You can do a whole lot of mitzvos through an agent; people who don’t know how to pray can still satisfy their prayer obligation just by listening – שומע כעונה. It’s the principle that facilitates everyone listening to the shofar, for example, without actually doing it themselves. But even during prayer, the go-to example of this principle, there has always been one section the leader can’t say for anyone else – מוֹדִים – the section on thanksgiving. At that point, everyone listening has to recite it for themselves.
As technical as it may seem, it’s actually quite simple; appreciation is personal. Maybe someone can help you with the Torah reading, but no one can say thank you for you!
The mitzvah of the night isn’t simply to tell the story; if we’re doing it properly, the mitzvah is to relive the experience and make it come alive personally. If that’s what we’re doing, we have to express gratitude personally, not via an agent or public reading, because genuine appreciation flows from the soul.
Parenthetically, this may shed light on why the Haggadah praises whoever expounds the details – כָל הַמַּרְבֶּה לְסַפֵּר בִּיצִיאַת מִצְרַיִם הֲרֵי זֶה מְשֻׁבָּח. The Gemara suggests that anyone who prays too much detaches themselves from the world because words are finite, so it is impossible to adequately praise an infinite God because the vocabulary does not exist. And yet, expounding the Exodus’ details doesn’t fall foul of this rule – הֲרֵי זֶה מְשֻׁבָּח – because whereas praise focuses on the other, the wellspring of gratitude comes from within.
Of course everyone has to personally participate – no one else can feel it for you! And of course there’s no limit. Because when we channel gratitude, we have to let it flow freely with no boundaries.