I live in a medium sized US city and my truck has been parked on a city street with tools in it, unlocked, for two years. Most people lock their doors here, but even in a city known for a medium amount of crime, it isn't really that bad.
A day later the car was broken into again. While the lock was still broken and no stereo in the car. Someone smashed in the side window and left the door ajar too. Nothing got stolenthat time around.