I do, partially because I've been socialized to be uncomfortable on a bike without a helmet, and because one time when I was riding at high speed physics turned off for a moment and the bike randomly lost traction, wobbling and then slamming my head down on the hard, concrete road. My vision was temporarily messed up, I only saw black and white, and white was much stronger, and my ears rang like hell, but I could get up and walk home. In other words, wearing a helmet saved my life. It was also the first accident I ever had with a bike, to anyone who is towing the "fag" line, you may think you're hot shit on a bike but it only takes one accident. One pebble on the ground,hit at the right angle, and bam, lights out. Of course, you could just walk. It looks less faggy than bikeriding anyway (less spandex). You can't do a cool guy explosion ignore on a bike.