One of the most forward thinking innovations of the Torah is the concept of Maaser Sheini, the “Second Tithe”. After 10% of the crops were set aside for the Leviim, a second 10% (now only 9% of the original crop) was set aside, not for others, but for the farmer and his family to consume, but only in Jerusalem. This might have been the first example of these government-authorized special funds and accounts that are so popular nowadays: The USA has the IRA and the 529 College Accounts. Canada has the RRSP. This is the government encouraging people to be smart and set aside funds for important times that will require cash.
Maaser Sheini was by nature an education fund. An inspiration fund. Moshe was talking to the Jews on the edge of the Jordan River. He knows that when the people cross that river, they will be living a life of the daily grind and hard farming work. At Har Sinai, they experienced a vision, prophecy. But soon, they would only be able to hear God on a daily basis. That’s why we say “Shema”, Hear O Israel, not “Look, O Israel”. But a few times a year, we would be given the opportunity to SEE, which is why the Mitzvah of pilgrimage to Jerusalem was called “R’iah”, seeing and being seen.
But who can afford to just take time off of work to spend time in Jerusalem? That’s where Moshe comes in and says, “Put aside 10% in a fund that can ONLY be CONSUMED in JERUSALEM.” This forces us to be able to afford it.
And this brought them to the Holy City, so they could spend time watching holy people doing holy things, learn Torah from them, spend time thinking about God and what He expects from us. This could be spent on YomTov, but any time a Jew wanted to go to Jerusalem, the personal fund was available.