said by NJSTECH :now that it the first expaination that makes sense
Most of those channels were in the 1000's because of the use of video traps. All of the frequencies these channels were on were not blocked by video traps. So if you have basic plus HBO, Cinemax, Showtime, etc you were able to receive them with a trap on the line. Since video traps are no longer needed because of the digital migration, these channels do not need to be duplicated.