While I understand the relation of surface finish and precision to the nurbs surface, I have explained to numerous vendors that I am not interested in high polish or extremely high precision surfaces.

The fact is most cam systems even now compute a toolpath based on a tesselated model derived from a nurbs model. Therefore, even though I may give a vendor a nurbs model, their machine is cutting it as G1 or straight line moves. So when they complain that they can't machine from from a triangulated model, that points out me they actually don't understand their own machining process very well.

Its quite funny actually when I asked to see sample G-code from one shop, to clarify this, they refused.

What I believe is happening is that most machine shops assume high precision work, and they won't stop and switch gears for projects that might be a little different from what they usually do.