Why do we need the Statement of Cash Flows? How does it help management?

In the Operating Activities computation: Why do we add back non-operating losses? Why do we subtract non-operating gains? Why do we adjust Depreciation Expense?

Explain how a firm can have a Positive Net Income on the Income Statement but a negative Cash Flow from Operating Activities on the Statement of Cash Flows?

Why are non-cash investing and financing activities mentioned in the Statement of Cash Flow? Give an example of an event that belongs here.