Because from a CAD user's perspective (that would be me) that's how they work.
A CNC machine takes a billet of material and cuts away anything that doesn't look like my part. What's left is my part.
A 3D printer hooks up to my computer the same way a 2D printer does, and lays down material on an otherwise blank space until my part is built. It looks like a printer, and acts like a printer, and associates with printers.
Quack.
I'm not in a rush, though. I'll know what you are talking about if you talk about a mashed potato printer. Or a concrete printer (those are pretty cool).
Fabber, or something like that. Ruin a verb (fabricate) to make a noun... It's the way, in English.
/johnny
So do small CNC mills. See the Roland line of MDX machines. My firm bought a Roland MDX-40 some years back for ~$10K, and it has paid for itself over and over and is still in use. Right now, I'm drooling over their MDX-50, designed for the dental market. FIVE-AXIS, sits on the table like a printer.......$30K. Just about perfect for the scale and volume of parts my company produces.
Also of interest is the QU-BD "open source" printer. Does both "additive" (thermal plastic deposition) AND "subtractive" (CNC milling) ON THE SAME MACHINE......fully assemble......$1700......"put it together yourself".....even less.