It was just that recording the Wizard Plane coordinates required caution. If there was something fishy about the Coordinates Earring, Duke couldn't afford to take that responsibility.
After weighing his options, he decided not to record the Wizard Plane coordinates. Instead, he considered going to a tourist-type plane in the future, where recording the coordinates would be more appropriate.
Numerous forces in the Wizard Planes have various types of planes, many of which have been developed for tourism and entertainment, where many Wizards have purchased properties and settled.
These planes, like Harbor City, are purely entertainment zones, except the whole plane is like that.
Duke's plan was to purchase a property in one of these types of planes, so before going to other planes, he could first visit these to cover his tracks.
Because entertainment planes are generally less regulated, unlike the strictness inside major Wizard Organizations, where high security is required.
