This is not necessarily true. The Supreme Court has ruled (see Deshaney v. Winnebego) that there is no constitutional right for police to protect citizens. As in, there is no private cause of action, under the Constitution, for police failure to protect you, unless the state very explicitly binds itself, such as if it is expressly stated in a protective order.

Cops do have an obligation in tort/state law/federal law to protect you in certain circumstances, as do rescuers such as firemen.

I know it seems like I am picking hairs, and I absolutely am not trying to support these Supreme Court decisions or sympathize with police officers. I agree with Breyer's dissent in Winnebego, that the social services of that county had a duty to protect the child from abuse upon instituting a protective order.

However, do you realize the absolute insanity that would have arisen from ruling that private citizens have a constitutional right to affirmative police protection? Millions and millions and millions of new lawsuits. It is not practicable for the judicial system. The correct avenue for this kind of change is through the legislature.