I always wear a helmet.
1. I actually find it more comfortable with my goggles than just wearing my goggles on top of my beanie.
2. Obvious reasons; safety. My mom is an ER trauma nurse, and my brother in law is a Paramedic. Wanna know about how all the crazy ways you could hurt/kill yourself are? Sit down at a family dinner with me. I've ruptured my spleen, broken ribs, almost punctured a lung (rib was poking into my lung but didn't actually pierce), 3rd degree burns, and actually almost had to amputate a foot after a volleyball game (long story)... So yeah. A helmet doesn't bug me, doesn't annoy me, even plays back my music. Why wouldn't I wear it.