According to The Hill, a briefing by senior intelligence officials on surveillance
programs failed to attract even half of the Senate, showing the lack of
enthusiasm in Congress for learning about classified security programs.
At the same time that many lawmakers have complained that they have been kept in the dark about the NSA’s far-reaching surveillance program, a majority of senators elected to leave Washington early last Thursday instead
of attending the classified briefing with James Clapper, the Director of National
Intelligence, Keith Alexander, the head of the National Security Agency
(NSA), and other key officials. 
The briefing also included the former chief judge of the Foreign
Intelligence Surveillance Act (FISA) court and Sean Joyce, the deputy
director of the FBI.

The Hill reported that the Senate’s last vote of the week was held shortly after noon and “many lawmakers were eager to take advantage of the short
day and head back to their home states for Father’s Day weekend.

47 of 100 senators attended the 2:30 p.m. briefing, leaving dozens of chairs
in the secure meeting room empty as Clapper, Alexander and other senior
officials told lawmakers about classified programs to monitor millions
of telephone calls and broad swaths of Internet activity. The room on
the lower level of the Capitol Visitor Center is large enough to fit the entire Senate membership, according to a Senate aide.