If the drones that people are reportedly seeing over New Jersey

Dennisville - If the drones that people are reportedly seeing over New Jersey are in fact surveillance devices—whether operated by foreign governments, domestic agencies, or the U.S. military—what purpose would their visible lights serve? Why would these unmanned aerial vehicles, presumably designed for clandestine observation or intelligence-gathering, be outfitted with lights that make them easily noticeable rather than remaining hidden in the darkness?