Why do police abandon police chases?

I recently have begun listening to a police scanner online and I frequently hear officers reporting they are in a high speed chase, but abandoning the chase because it is too fast??? Doesn't this send the message to the bad guys that if you drive erratically and dangerously, you won't be pursued? Why do they not take aggressive action to disable the vehicle and/or its driver? If the vehicle is being driven dangerously and will not yield to law enforcement, shouldn't lethal force be used to disarm the threat?