Courtesy?

I was in the basement studying earlier so I didn't disrupt my roommate, who was trying to sleep. I was down there for maybe fifteen minutes before two other people came down. I wouldn't normally have a problem with this, but these two people were being really loud and playing their music up loud and talking on the phone, but on speaker phone. After about another fifteen minutes, I had had enough. I couldn't focus on my studying. I have one test and two quizzes tomorrow that I have to study for. So now I am back in my room.

I don't understand how some people can be so loud if they can see that someone else is trying to study. Do the people my age know what courtesy is? I don't understand how the people my age act the way they do without common courtesy to others.