I've been on both sides of this. As a lawyer who sought and obtained them, and as a former spouse that obtained one against my ex who stalked me, blackmailed me and otherwise made my life a living hell for having the nerve to leave him. They are, in short, not worth the paper they're written on. And perpetrators know it. In my own case, my ex violated it several times and each time a cop (male, interestingly enough) would go have a "chat" with him.
Just about a month ago, a dog park friend of mine wa shot in the shoulder and her 3 children were killed by their father/her ex husband. He was known to police and the courts as violent. I can't tell you how many "pieces" of paper had been issued telling him to stay away.
The truth is we have to do better. The system has to start taking those who have suffered domestic violence and are in real fear for their safety and lives seriously.