As part of the cultural catalog of his people, Nephi tells us that he imparted his knowledge to them. He teaches them what he knows of building, woodwork, and metalwork. Interestingly, he specifically teaches them the working of brass and steel. Certainly the steel should have been sufficient for the making of military-quality swords, which argues against the note above. However, while he imparts the knowledge, he does not necessarily indicate that the knowledge was useful. While it was certainly useful for buildings and woodworking, he notes only of the precious ores that they were in great abundance. Of course it is speculation, but perhaps the ores for the other metals were not as readily available.
Those ores and metals are known from Mesoamerica, but were not in wide use. It is possible that for the Nephites as well as for the rest of Mesoamerica, the abundant ores and therefore the concentration of metalworking was in the precious metals, with the other metals being of lesser availability, and therefore of lesser utility. This would have been particularly true of a small band of people with no surplus trade goods sufficient to acquire valuable but rare metals. The "precious" ores were apparently easily found.