Why? Layer categories have more power than just naming a single layer. So what if the layers are numbers instead of names, you get used to the format. Layer categories add more flexibility because you can change multiple layers with a single word (category name). Also, you can have multiple categories assigned to a single layer.
My guess is that you are new to NX having come from some other CAD system. Tell us more about why you think the NX layering functionality should be changed and what benefit you see from the change.
For reference I have used UGII/NX from 1987(UG2 ver3) to 2010(NX4) and Pro/Engineer since 2001(2000i2) upto now(WF4).
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