Because anyone who attempts to take justice into their own hands will have their life destroyed by the incompetent backwards judicial system. The only cases where this kind of reaction should be expected, on an individual level, are cases where someone's child, especially if it's their only child, is killed. At that point a parent's life has already been destroyed and the threat of the law is no hinderance to them doing the needful. Unfortunately, in cases where exactly this has happened, not even such parents stand up an act.