Aside from all the things you couldn't make with that approach, 3d printing enables something like the classical lazy programmer.
You can take an open source part, and print it (like using an open source project or library instead of reinventing the wheel). Also, you essentially need only 1 tool to make this, and one material. The effort and time is much smaller, so you can make many more things. You can iterate and improve.
For a rough parallel, you're guy who wants to write a new web app in C. Nothing wrong with C, and without it, there would be no web apps, but the guy with the scripting language and framework will probably smoke you in getting it out the door.
You can take an open source part, and print it (like using an open source project or library instead of reinventing the wheel). Also, you essentially need only 1 tool to make this, and one material. The effort and time is much smaller, so you can make many more things. You can iterate and improve.
For a rough parallel, you're guy who wants to write a new web app in C. Nothing wrong with C, and without it, there would be no web apps, but the guy with the scripting language and framework will probably smoke you in getting it out the door.