Music somehow has a way of influencing just how we actually think and feel. The right kind of music can make us feel invincible and let us take actions that would normally be difficult, or at least challenging to us, while the wrong kind can make us feel inferior and sometimes even powerless. And unlike most other forms of stimulants that can alter perception, music seems like a better alternative, considering that we just need to listen to it.
Anyway, to this effect, people in the modern age have come to rely on headphones and headsets to make their musical experience even more worthwhile. After all, keeping your music to yourself can have two benefits. One, you reduce the chance of being a nuisance to others in case the music you're actually listening to isn't the kind that the people around you might not want to hear. Second, by keeping your favorite music focused on yourself, you get more of its power-up effect to yourself.