People know when they act irresponsibly. But their knowing does not stop that type of behavior.
Knowing the cause for behavior may be interesting, but has nothing to do with changing that behavior. Until responsibility is accepted, the person will not act differently—even when the person knows the reason.
Therefore, rarely ask a person why the behavior occurred. “Why?” implies that the reason for the behavior makes a difference—but it does not. Knowing or knowledge does not lead to behavior change.
Rather than asking “Why?” a more effective approach would be to ask, “What are we going to do about it?”