I'm not positive but I believe that the wires are installed the same on all models regardless of options, so I'm guessing it's for something like a rear window defroster. Probably goes to an empty relay slot that would have controlled the defroster (or whatever that switch was for).
Speaking of lights, you might be factory wired for fog lights. Look under the wheel wells for wire looms that lead to an empty connector. My TJ has them even though no factory fogs or even a fog switch. Good luck!