I don't know that anyone "needs" an electronic copy (but then, does anyone "need" a physical copy?), but it sure is convenient to have one on my hard disk. It's always accessible, and searchable.
I'm not an expert on the matter in any sense, but there's been a discussion recently, with
David Pogue on one side and
Adam Engst on the other. So, at the very least it's not a clearcut matter where one side is definitely in the right.