I'm one of those persons!
When I'm by myself, as for some reason it's deemed rude to listen to music while out with the kids! For me, earphones are a god-send, because I've never been good at talking to strangers. And I'm old enough to remember the world before mobile phones. It's not in my nature. A trip to the hair-dresser is hell for me, as I've got nothing to talk about with that lady. A waiting room? I still get to spend a lot of time waiting for my son at his activities, and there are other parents there... I cannot face the idea of talking to strangers, so I'm glad to be protected by ear-phones... The only thing I regret is that head-banging on the street is not socially acceptable.
While out with children is the only time I might consider wearing earphones!
I love to talk and feel very awkward if I'm in a room/lift where there is silence. We used to have quite a tradition here for chatting to strangers but sadly it's quickly dying.
As to headbangers, in the other sense of the word, we have loads of them in Dublin so you'd feel right at home here:)