Not every Hyrkanian can build Hyrkanian Armor, not every Cimmerian can build Cimmerian Armor and so on and so on.
But feel free (Funcom too) to visit the Official Conan Exiles Wiki if you look for a specific type of Armor or look at the Armorers page to get a full overview in one look (sortable by your needs). A full overview for any NPC you can check the Thrall’s page.
Edit: But you are right in some other way. Than Hammerblow like Chelkus the Smith and Diana Steelshaper is useful for nothing special. That means these poor people can only craft the standard recipes like all others and nothing special related to their race or faction.