You have to change the Customer Default 'Change View Orientation' under 'Sketch -> General -> Tab: Session Settings
In NX 7.5 the option "Change View Orientation" in the sketch preferences dialog only works for the Sketch Task Environment. In NX 8.5 the option was made to work for Direct Sketch.
There is no option to do that in NX 7.5. The only way is to right click and select Orient View to Sketch or by Pressing (Shift+F8) command.