Mishnat Hashavua: Ma'aser Sheini 3:1

What religious obligations can be outsourced, and which must be personally performed?

One should not say to his colleague, “take these [second-tithe] fruits to Jerusalem for me, and keep a portion for yourself.” Rather, he may say, “bring them up and we will eat and drink them [together] in Jerusalem.” However, they may always give [second-tithe fruits] to one another as gifts [in Jerusalem].

Comments :

The Israelite farmer was required to pay an elaborate series of gifts to the poor and the clergy (Kohen and Levite) before enjoying his produce. The “second tithe” was either produce or its cash value (plus 20 percent) that could be consumed only on pilgrimage to Jerusalem. Our Mishnah imagines a farmer who wishes to designate an agent to perform this mitzvah on his behalf. This is forbidden, but the Mishnah provides for Israelites to assist one another in transporting the second tithe to Jerusalem and also to share the fruits freely with one another.

Questions:

Why can’t a farmer pay an agent to take his produce to Jerusalem? Why must he complete the pilgrimage and eat his own fruit in the holy city? Should we limit the extent that we pay others to perform mitzvot on our behalf (e.g., building a sukkah or saying kaddish), or is the essential obligation fulfilled either way? What social benefits are bundled into this mitzvah? What would Jerusalem have been like during a festival where all farmers were obligated to consume so much food together?