It would be wrong to waste the nutrition of the deceased in this situation just as it was proper for those in the Alive story to turn to cannibalism to survive . They were n't killing people to provide the food supply ( though it would certainly be a valid concern as stated in the movie ) so the real question is , why was it treated as such a big secret that Soylent would kill over it ? They needed better PR people to just sell it outright and save the suspense . But then , that would n't be a good movie .

Question: What may be the reason for Soylent killing ?
Answer: In order to obtain eternal youth .In order to survive .in order to remain the strongest .In order to remain the fastest .