it doesn't make sense if you're not prepared to put a modicum of thought into it. if you're standing for example on the side of the road, you look to your right, you look to your left, and if one way you get a blast of headlights the chances of you then seeing a cyclist without lights are diminished. leaving aside the issue of evening and night vision, when people prepare to cross the road in the dark, they will look for approaching hazards with lights - cars, buses, police vans etc. they may not focus on hazards without lights - and why should they, when the highway code is so clear on the matter? if, as beesonthewhatnow tells us, cyclists want to reach their destination alive, surely they should equip themselves with the necessary safety equipment for that. not endless sorts of body armour, just a simple set of cycle lamps ought to prevent many accidents.