I don't think as to why means anything more. It's a rather unusual term except in poetry where you need a bit more emphasis - or a couple of extra words to make the lines line up. Good explanation of why it's optional in this case, although i'm not convinced that reason is the only reasonable antecedent of why. For example, the explanation why is a common usage,. Why is used here as an interjection.
—used to express mild surprise, hesitation, approval, disapproval, or impatience I have flunked the exam, that is why i am attending coaching classes. I have flunked the exam, which is why i am attending coaching classes. Is there any change in the meaning of sentence. Why is it that everybody wants to help me whenever i need someone's help? Why does everybody want to help me whenever i need someone's help? Can you please explain to me.