Most telling was Senator Tim Scott of South Carolina whose excuse was that he was going to be in South Carolina at that time.
Distance Charleston to DC (according to Google Earth) 531 miles. Distance Passenger jets fly in an hour (According to ChaCha.com) 587 mph. Yes, of course, there's check in, baggage, security gates, etc. and then booking a room in DC. Oh Wait! Tim Scott is a US Senator who should have a regular place all settled so he can attend the Senate, right?
Tim Scott would be the currently most important symbol of how far we've come besides the President himself. But even he had to play by the GOP rules.