In the US, cops are legally allowed to just ignore you.

There was a case in Colorado I believe where an estranged husband kidnapped his kids from their mom. The mom went to the police but they kept brushing her off. After while the dad showed up to the station with a gun, promptly got killed, and then the kids were discovered dead in his car.

It went to the courts, and courts came back with "yeah they don't HAVE to help you." Of course this is overly simplified, but there's case law in at least part of the country now that allows cops to ignore anyone at their discretion because they're on dinner break or just not feeling it.

Also in the US, cops can tear your car up on a minor traffic stop because they "smelled" something. If they search your vehicle for whatever reason, they can decide they want to throw all you stuff out on the road, cut open your upholstery, take door panels off, etc. And if they don't find anything? "Have a good day sir, get your shit off the road it's a public safety hazard." Then drive off leaving you to pick up their mess. And yes it has happened, and no not just once.

There was a case in New York where a guy was going around stabbing people. Cops posted up looking for him of course. Guy on the subway got stabbed nearly to death, a bystander tried to help the victim and took the criminal off-guard. Cops came in from the operators cab and subdued the criminal. They were watching the whole thing from the operators window and didn't help the victim until they saw an opening created by the bystander. Literally watching a guy on his way to getting stabbed to death and only decided to intervene when they felt like it.

Also the Uvalde school shooting. Just hanging out in hallways while kids get shot, waiting for the danger to clear.

Also George Floyd but at least some amount of justice has been served there. But I'm highly skeptical it would have came to that if the case wasn't as well-known as it was. Shit happens all the time. They have a term they love to bust out for minorities who are acting out of line. "Excited Delirium": look it up.

I could go on, but I think you get the idea. They "can" help, but totally not a requirement.