There are tons of ways to use 3D printing making molds and tooling. We do it in my industry all the time. There's potential to make plastic parts in small quantities but in large quantities it's faster and cheaper to injection mold. Metal works best when worked and heat treated. It's hard to do that with 3D printing. We still use a lot of forgings that are NC milled or lathed to final shape. NC machines are used to lay carbon fiber tow for pressure vessels and other things, but it doesn't quite fit the image of "3D printing" you might have in your head.