Just a guess, trying to remember what I read about that myself....I think it they said it has somrthing to do with if they see you pick it up, they may think they are supposed to clean it up....leading to poop eating you read alot about. Again, I may be way off, I can't remember where I read about the subject. Good luck with your pup!
When they see you clean it up, they relate it to when their mom used to clean it up. they then think you are SUPPOSED to clean it up...or something along those lines. I can't remember exaclty either...I am sure that Redyrerottweiler or Doberluv or Grammy (bubbatd) would know the exact answer though!
Altho dogs if properly raised are naturally clean animals who WANT to eliminate away from their den and sleeping area, if they see you constantly clean up after them, they stop worrying about being clean.