

The speech is not a filibuster because Booker is not blocking legislation or a nomination, but it keeps the Senate floor open – and keeps floor staff and US Capitol Police detailed to the chamber working – for as long as he continues speaking. Lawmakers had concluded voting on Monday before he began his remarks.
So is there any reason why the others Senators shouldn’t just leave?
No, not in the slightest. They will try anything and everything to get what they want, and usually succeed because there aren’t any actual safeguards in place.