I genuinely think Spotify and Netflix, and other streaming services, have been the biggest blow to torrent sites. For the average user, it's just so much easier to pay $10/month (or even less when you share your account with friends) and get easy & user-friendly access to the content (in a way that happens to be legal).

10-15 years ago, before Spotify/Netflix, people used to say: "As long as it's easier to acquire things illegally, people will continue doing so," and I think that has really been shown to be true.