Supreme Court precedent in Deshaney v. Winnebago County Department of Social Services (1989). In that case, a young boy was repeatedly abused at the hands of his father, something that county Social Services was aware of, but made no effort to remove the child. His mother sued once the four-year old entered a vegetative state, and the Court ruled that that the state did not have a special obligation to protect a citizen against harms it did not create.
Based on these precedents, Lozito was told in the New York City case that “no direct promises of protection were made” to him, and therefore he could not sue the police for failing to come to his aid. In other words, the police do not have to act if someone is actively being harmed, they do not have to arrest someone who has violated orders, and they do not have any obligation to protect you from others.
People are still expected to call the police, and many still do, especially given the lack of alternatives. But to criticize their effectiveness in solving crimes in the aftermath furthers the propaganda: It assumes that the police are acting in the interest of the public, when there is no precedent that says that they have to.
Police reform activists have posited that the purpose of policing is not to protect the public, but instead to maintain the status quo that keeps capitalism alive. The first modern-day police were slave catchers; their only interest was your body for their profit. Whatever their true purpose, the legal fact remains that public benefits from policing are incidental, at best.