I only knew 2 Black DZs over the years. And only idiots asked them why they didn't pledge AKA because they are Black and (*gasp*) seem to like pink and green.
Anyone with a head distinct from their ass knew that these young ladies (were cool as a fan but) did not feel a cultural connection with the Black and African Diasporas and therefore would not join a BGLO. That's not the case for all Blacks in the NPC and IFC, but it was certainly the case for them.