There's a reason that evil empires with a "leave no survivors" policy were so successful. It's because they left no survivors. They burnt the villages, they salted the fields, they made sure that even the fleeing refugees hiding in caves had nowhere to go and no food to eat. They did not let random wagons pass by unscathed merely because they didn't look like they had any enemies in them.
C-3PO: If we get shot down, I'm going to kill you.
Lieutenant Hija: There goes another one.
Gunnery Captain Bolvan: Shoot it! Shoot it!
Lieutenant Hija: But it has no life forms, sir.
Gunnery Captain Bolvan: Oh right... because there's no such things as sentient metallic beings with no life readings in this universe...
Lieutenant Hija: I'll just shoot it down, shall I sir?
Gunnery Captain Bolvan: Good idea, that man.
Lieutenant Hija: Huh. The guns aren't working. They must have short circuited.
R2-D2: Oh yeah, baby.