Sadly this is true but it isn't the copper on the beat that gives up. They are told to give up by the control room. IE if the rider takes off their helmet they will most likely call the pursuit off. If the rider enters a build up area with lots of peds the pursuit is called off. The problem is if their is a fatality of the rider being chased by the Police papers like the Guardian make the thieves out to be heroes being run down by a corrupt police force. So sadly they now have to let them go most of the time encase the thieves hurt themselves.