Maybe another part of this is habit? I've been riding bikes my whole life (well, since age 3 anyway ) and motorcycles since age 12. Back then (60's and 70's) no one wore a helmet for anything so I never got in the habit. Fast forward to 2011 and I live in one of four states with no motorcycle helmet law so I've never been compelled to wear one. I tend to wear one (MC helmet) when it's cold or windy, and I'll put on a bike helmet if I'm riding out in the country... most of the rest of the time it never even occurs to me.