And another possibility I considered is that perhaps the President after eight years of the same faces came to some sort of causal attitude, but given the office the President holds, I don't think so.
Put it this way--we always stand when a judge enters the courtroom to start a session (at least that's how it was when I was on jury duty). President enters the room--stand until asked to be seated. Just a matter of respect for the position, even if you may not like the guy.
Too bad the liberals forgot that.