User blog comment:The Milkman/Reaper Logic/@comment-2127388-20120425203841/@comment-1900300-20120426032401

I could think of a lot of jokes to answer that but the simple answer was he didnt need to. Maybe the Reapers are as oblivious as to what they are doing as people are. They know why, but they dont know something is directing this belief. So them it would seem like unquestionable instinct.

I kinda wish the ending was more about the Reapers being as much slaves to the Cataylst as we are and Harbinger actually helps Shepard so the Reapers could be free. Paragon agrees with the promise the Reapers would not return or Renage takes the place of the Catalysis to enslave the Reapers himself.