If you've never walked 45 minutes from work to your house through rice paddies in a torrential downpour while listening to The Smiths and screaming along, you should. Never mind the occasional old lady who looks horrified at your atrocious squawking and wild umbrella waving, it's your world and no one can hear you sing if you can't hear them say anything.
I love headphones invincibility. It's why I pick my nose shamelessly on trains. If I can't hear them, they can't and are not judging me.