The modify "they must maintain a physical presence" failed because republicans only had to keep a physical presence of the senator that had the floor and his relief team. The Democrats had to maintaina physical presence of all 55 senators.
To kill it means the results of the majority will be judged by the people that elected them. The filibuster inreality is a no faith vote for the the American people. Which just happens to be the republican core principle, they must be lead by the chosen.