Because after 18:45, it was just too dark to see. I could hear the beeps, and even pinpoint on the coil, only I wasn't sure where exactly the black coil was.......So the the Garrett Pro Pointer saved the day, or should I say night, by giving off some light from the tiny LED to see my AT Pro screen, where the coil was and even when the coin got popped out using my trusty screwdriver. 