" if you want something that can be manufactured that's not good enough"

People design all sort of buildable things in SketchUp and it's just about dragging polygons around.

You _may_ need accurate surface if you run your model to CAM.

But to this day lot of manufacturing is still done via drawings and there the only thing that matters is that can you draw some type of lines and attach clear dimensions to them. So the shapes don't necessarily need to be accurate for all flows since they are more like topological hints to the person reading the drawing rather than accurate replica of the thing to manufacture.