Part of it is hearing loss from constantly blasting music.On a related note, what is up with the rudeness of using a speakerphone turned ALL the way up in public places. I was sitting at the bar of a fairly nice restauraunt (Pappadeaux) trying to enjoy my dinner, and there were to guys in their 20s across the bar from me. One appeared to be facetiming his girl and he had the volume turned ALL the way up. And of course he's talking louder than he needed to because its not up to his ear. I could hear the entire conversation from across the room. And it was loud enough that there was no way for me to politely ask him to turn it down without raising *MY* voice and appearing aggressive. So I just shook my head and let it go.
Part of it is being intentionally disruptive and irritating in the hopes of pissing someone else off enough to give them an excuse to be violent.