The United States has 574 federally recognized tribes. They have treaty rights, sovereignty claims, land disputes, water rights, and a centuries-long relationship with the federal government that includes a substantial amount of bad faith on the government's side. None of that relationship is currently represented in the Cabinet.
A dedicated Cabinet seat for Native Peoples would give tribal nations a voice at the table where federal decisions are made, not advisory, not symbolic, but a full Cabinet-level position with the standing to shape policy directly.
It's a straightforward acknowledgment that the relationship exists, that it matters, and that it deserves representation.