#1, They're a long-standing tradition in South Africa that dates all the way back to 2001... when a plastics company developed the horn, knowing how much futbol fans, particularly those in Africa, enjoy annoying everyone else.
Have you seen the stupid vuvuzela button on YouTube? They actually spent the time and money and programming skills to make a soccer ball icon on the video player that plays a vuvuzela sound when you click it.
I did enjoy The Daily Show, when John Oliver was interviewing a South African official who was defending the horns, and every time the guy tried saying something, John blew the horn in his face to drown him out XD