BitTorrent has proven to be an ideal tool for pirates. The protocol’s decentralized nature makes it impossible to interfere with transfers between users. Torrent sites and indexes are the only weak link in the chain, but there are novel solutions to that ‘problem’ as well, it appears.
BitTorrent is often praised for its decentralized nature. The file-transfers take place between users and there’s no central service required.
That’s also one of the main reasons why pirates embraced it.