They're just smarter than we are. Two thirds of the applicants to the our prestigious local university are denied. Cyclists sans lights are very common, the vast majority obviously students bright enough for admission. Evidently they're so bright they regard lights unnecessary. BTW our local bike club offers free lights. My worst nightmare = taking out some dim bulb on a bike. I've had a few close shaves and the opportunity last spring to encourage the rider beside me at a traffic light to please get a bike light. He agreed to do so.