Real answer? Because people around them don't get angry and tell them to stop doing it.
I do blame them for being insensitive idiots but I also blame others who are afraid to tell them what they think.
Im not any better. I recently endured a train ride of 5 hours in the seats right behind a family with kids who were yelling, screaming, jumping... Everything, as if they were at home. Parents were just as loud, talking and screaming over the loud noise of their kids.
I escaped it by going to sit in the restaurant wagon, it was much quieter than our seats.
Im super interested in ghosts so I would rather stay somewhere where it's haunted. :) I wouldn't be able to sleep and would probably be scared all the time though.