To understand the import of these verses we must approach them on two levels. The first, and most important, is the reason that this curse was given. The second is the particular nature of the curse itself.
One of the greatest iniquities of the people is the abandonment of the egalitarian ideal from the Nephite gospel. These are a people who have accepted not only wealth, but the social distinctions that have come from wealth. Their love of the display of wealth has led to the creation of ranks in society where people will esteem themselves better than others based on their ability to mount the wealth-displays. In this curse, the Lord deals with the heart of the matter. The problem is the wealth and their desire for it, and so the Lord declares that he will take it from them. Should they attempt to preserve it by burying it in the land, the land will take it away. This conceptually echoes Nephi’s statement about the superiority of the dust of the earth, which obeys God (Helaman 12:7-8). It is also a rather literal expression of the imagery with which we are familiar from the New Testament:
19 ¶ Lay not up for yourselves treasures upon earth, where moth and rust doth corrupt, and where thieves break through and steal:
20 But lay up for yourselves treasures in heaven, where neither moth nor rust doth corrupt, and where thieves do not break through nor steal:
Note how Helaman 13:19 does ask the people to lay up treasures unto the Lord, but the curse removes the worldly treasures that are hidden up for the purposes of stockpiling them.
The second aspect of these verses is the specific cursing of the earth so that it will swallow up the treasures. Verse 21 indicates that the time when the Nephites might bury these treasures is when they are fleeing an enemy. Why would they not simply take them? Of course they would be too many to carry, and when life is threatened it is more important to take the things that will sustain life. We must also remember that Mesoamerican was a barter economy. These treasures were objects, not money. They have great bulk, and so they would be left behind in such a flight. The cursing of the ground is that it would swallow them up and not return them.
Archaeologists are more than familiar with this particular cursing of the ground. The native of the climate in Mesoamerica is such that many of the treasures of the ancient world, those things that would be treasures to us even if they were ordinary to the ancients, have been swallowed by the earth. This cursing is rather literal.
Lastly, we should note that this burial of the treasures would come when the people flee (verse 21). These conditions will come in the next great Gadianton confrontation where the people of the southern Nephite lands which are the specific ones Samuel mentions, will gather up what they can and flee to the north for common protection (see 3 Nephi 3:21-23). The curse tells them that when they do, there will be no riches to come back to.