Given that they're almost all criminals killing other criminals. there's not too much to incentivize the police. If two meth dealers want to shoot each other over $30 then I'd say go right ahead.

Plus add in all the 'sniches get stiches' hood mentality, it's not like anyone's going to offer any help in naming suspects. Half the people in those area see the murders as a sign of a job well done, about their drug-selling crew showing how should be shown 'respec' for being such towering leaders of industry