I've never actually seen a cockfight. I think it's really adrenaline-filled and I might enjoy it. I don't like violence, but I think it's compelling.
Let's remember that violent encounters have always appealed to mankind, from Roman times with gladiators to the present day with martial arts, boxing, and MMA.
I don't think it's strictly related to addiction; gambling in general is addictive, so cockfights are just one of the many bets you can place.