The Lord directed Israel to erect or to perform various memorials, and memorials bring to the memory some significant event of the past, usually in a nation’s history, but the history of Israel did not exist for itself, rather whatever Israel experienced, the Lord wanted it for the world. The stones that the children of Israel took out of the Jordan River served this purpose,

And those twelve stones which they took out of the Jordan, Joshua set up in Gilgal. Then he spoke to the children of Israel, saying: “When your children ask their fathers in time to come, saying, ‘What are these stones?’ then you shall let your children know, saying, ‘Israel crossed over this Jordan on dry land’; for the Lord your God dried up the waters of the Jordan…that all the peoples of the earth may know the hand of the Lord, that it is mighty, that you may fear the Lord your God forever” (Joshua 4.19–24).

Yes, the children of later generations had to know the reason for the stones, that they testified of the unique way that the Lord brought a few million people across the Jordan and into the Land of Canaan, but the world also needs to know of this event, because it shows that the Lord keeps His promises, specifically the promise to Abraham, which ultimately finds its fulfillment in Jesus Christ, who is for all the world (Galatians 3.8).