Sasuke: People think of him one dimentionally, rather then a huge grey. He is neither a villain, nor a hero. He is lost. His heart is the only compas the Shinobi world has given him. He is not a crazy maniac, though he has had pretty crazy moments.
Because the situation never presented itself. If Orochimaru were to get put in that situation by Kishi, do you think Kishi would have just let Oro get beat up, not knowing where is opponent camouflage into?
Even though it hasn't been shown, Kishi is very factual when it comes to animals and real life.