Why don't cops shoot?

I'm watching tru tv and in the past hour i've seen 8 police videos of men who run to their vehicles and drive away to escape. All these men caused thousands of dollars of damage and a couple of pedestrians were hit. One almost hit children crossing the street. If I were a cop I would unload my gun as soon as the guy started to take off. personally I don't care about his rights and won't let the criminal put any person or property in danger. Why don't they shoot and prevent this $hlT from happening?