When the OBC recording of Memphis first appeared on CD, it wasn't by a real record label. I assume it was done by the show's production team. That decision probably doomed it from being nominated for a Grammy. Eventually it was re-released by Rhino.
Looking at the list of nominees from '59 to today, most of the choices are very conventional, which does make sense. However, I think it's also obvious that their has been very little input from anyone with a real depth of knowledge about Musical Theatre recordings in the overall selection.