Because subordinates may be less qualified to judge whether the action is a crime or not. This would basically place the onus on the lowest level of the hierarc

Because subordinates may be less qualified to judge whether the action is a crime or not. This would basically place the onus on the lowest level of the hierarchy in determining whether an action is ethically acceptable. People are frequently trained not to question their superiors judgment and to just follow orders. I'm not saying this is right, especially when in some cases the person executing the order may be in a better position to understand the implications, but it puts a conflict between expecting subordinates to second guess every order they're given, which isn't healthy for a well functioning organizational hierarchy. It also puts the person who would otherwise be "just following orders" at risk if they make a misjudgment, discouraging them from disobeying even if they suspect what they're doing is unethical.