Pencil vs Computer

One of my friends' father is an old engineer. Last week when I asked whether they can produce a kind of stainless steel art cup, he provide the design and cost right after we describe the requirement. When I looked at the picture he provided, I can't believe it's drawed by pencil, very neat and tidiness.
I ever saw how the constucture engineer work, they draw blueprint by the 3D software on the computure, then printed it by the large printer. But it's much more amazing that man can draw a product picture like this by hand.