To a degree this is true, but a perfect example I just ran into today is this: I've got 3 sonar range finders to mount on my robot chassis which has been made from aluminum- I could painstakingly hand craft three holders out of wood or metal, spending at least an hour or two per holder, or I can find a model on the Internet, modify it to fit my application and print all three at once in under 90 minutes. You shouldn't be 3D printing everything, but it is INCREDIBLY useful for small part fabrication.