I'm a publisher for >10 years. At first I used the policing services, but I stopped worrying about torrent sites and other low-grade pirates when it was clear that A) most readers don't use them B) site operators are located overseas and don't give a FF about U.S. C&Ds and C) I have better things to do with my time.

As for pirates on Amazon itself, or other major marketplaces: That's a different story. I have a registered trademark on Amazon Brand Registry and do use it to find bogus copies and copyright violations (usually in the marketing copy or cover images) to get them removed, with about 60 or 70% success.