There are not exactly wires inside nurbs only curves generator!
You can make that ;) Hide the faces!
A sphere gives only an arc of circle for example!!!
Here a box that can be considered as a wire but...that is not!
Hi Anders - because MoI has a "hidden line" display with hidden lines displayed in a faint dashed line style and also accessible for selections, it doesn't really have a separate wireframe mode. Instead of switching to wireframe mode you instead just turn hidden line display on or off (View > "Display hidden lines").
But it is possible to hide faces like Pilou shows and there are also a couple of scripts that you can set on keyboard shortcuts for doing some other similar things localized to just the selected objects: http://kyticka.webzdarma.cz/3d/moi/#SetSelectedObjectToWireframe