Why hasn't this series been shown again ?

This was one of the best spy genre movies to have ever come along and yet to my knowledge it hasn't been shown since its initial airing. Why not ? Along side Alec Guiness' two series of John Le Carre works in the 70's this was the most gripping spy drama ever on TV. Michael Keaton, in the role of James Angleton, was particularly memorable in portraying a character who was infamous in the history of the CIA. I still recall portions of an interrogation scene in which Keaton, using the idiosyncrasies and guile of Angleton, was simply mesmerizing. Please if anyone has a shred of decency tell me if it is being aired.