The word "why" can be used to request information or it can be used to express blame. When another asks you a question using "why," it could be helpful (for both of you) to become aware of which "why" they are using.
"Was that a curious 'why' or was it a blaming 'why'?"
My girlfriend asked me the question, "Why didn't you decide earlier that I was your one-and-only?"
I paused and thought. Then in a light and playful (non-defensive voice), I asked (curiously), "Was that a curious 'why' or was it a blaming 'why'?"
She smiled and responded also lightly, "It was 80% curious and 20% blaming."
So then I said, "I will respond to the curious 'why.'" Which I then did.
I could have also offered to respond to the blaming part.
I could have asked, "Would you like me to apologize in some way for not deciding earlier that you were my one-and-only?"
Or I could have offered to allow her to blame me and I would do my best to just listen, asking her to express her blame more fully to me until she felt that I had heard her completely.