[Blarg]

Actually headphones are a big cause of hearing damage supposedly, because people tend to crank it when wearing them, and don't realize how bad that's hitting their ears.

My guess is that part of the reason it's so natural to really crank your music when you have earphones/headphones on is because unlike hearing music normally, there's a tendency to find sounds besides the music less acceptable, so we crank it high enough to hear only the music, or just hear very little else. You don't need that same volume to feel like it's loud enough without headphones, because youi don't except the music to completely coccoon you and block out the world. So we crank it to envelop ourselves in our own little music world.