Incentive
Most of our laws, society, etc. works on incentive. Don't kill this person because you will go to jail for a very long time. Don't steal that box of chocolates because you'll have to pay a fine, possibly go to jail. Don't steal that MP3 because it's illegal and you could have to pay a $25,000 fine per piece of music.
But obviously it doesn't work does it? Nobody thinks about the possible fines when they copy a CD, or tape from the radio. If I was at the stage for some reason I was about to beat someone over the head with a brick, I wouldn't be thinking "gee, shouldn't do that, I might end up in jail". I'd definitely be thinking, I can't do that, this person might die.
Everyone does things against the law or that are dangerous to them and always will. Speed, take 'illegal' drugs, drink to much, fight, swear in public, be racist, be sexist, be homophobic, smoke, use mobile phones, not exersize.
People begin to stop when they've experienced the possible results. People may be a little more careful about speeding after paying a fine (except they're so pathetically small, they usually don't). They may not drink and drive again if they crash a car, possibly hurt or kill a loved one. But they won't change until this has happened. 'It won't happen to me, that stuff happens to other people, people on the news.' They might stop smoking if they get lung cancer.
Education on these things will change a few, but not most. The thought that this stuff might (will) happen won't change them until it does.
Or maybe it's just me?