Parker presenting might have been a bit of a challenge. She can't present for Leading Actress if she's nominated in that category again, and she and/or the producers may have found it awkward for her to present for Leading Actor, given that David Morse was nominated but was not expected to win.
Andrew Burnap is apparently filming Disney's live-action Snow White in Germany. Maybe he couldn't get the time off to come back and present.
Completely weird that they would pair Astin and Harden and then NOT announce that they are in a new CBS show together. After all, that's the whole point from the CBS marketing perspective.