Good question. Before I go any further, let me assure you and other readers of this reply that I'm not an expert. I have no formal training in this area. My contact with these women has been as an intake interviewer at a local non-profit food bank and some time spend at an abused shelter working with therapy dogs.
Having said that, here is my limited experience: The abused can take out a legal restraining order against the abuser. But, when seconds count, the police are only minutes away. Assuming the abused is not living in a shelter, the abuser can visit the abused, do lots of damage and be gone in a short period of time. The abused will be traumatized by this and may or may not call the police. Especially if the abuser has threatened even more mayhem if the police are called.
If the police are called, they will respond, call EMS if necessary, make a report and make an effort to find the abuser. Like finding a needle in a haystack.
If the abused is living in a shelter, the abuser is not likely to visit but there are still ways for the abuser to make the abused's life a living hell. If the abused is working, the abuser may call work and make threats. The abuser may wait for the abused to leave work and make threats/attack the abused then.
It's a real problem. The goal is to make the abuser's life as difficult as possible.
I could write a book, but won't :)
I totally agree with your assessment. Especially about the police being only minutes away when seconds count.
In an ideal world wrongdoers would suffer or at least be greatly inconvenienced by the wrong they do. Sadly, we know it is often their victims who do so. This especially true when it comes to domestic abuse.