I just don't find enough uses for it to justify the floor or bench space for the machine. In subtractive manufacturing where one takes away material I can work in metal, plastic, and wood. I can cut, plane, sand, shave, drill, tap, or die-cut, and if I pick up one of those tabletop mills, I could mill and otherwise create channels, and these can all be done in three different materials.
The problem is that a cheap 3dPrinter can do shapes which would require 5-DOF CNC. These are very expensive. So you can use only plastic in a 3d printer but you can do very complicated shapes. With a cheaper 3 DOF CNC you can use also wood or metals, but the shapes you can produce will be simpler.