The material doesn't need to be hidden from the world (ISP at most) because it's already public material. It includes checksums in the protocol at a more appropriate frequency.

Plus (some) SSL has only just become hardware accelerated. It's only now or in the next few years that someone would consider SSL in torrents - just for hiding from ISPs. Still too many other problems. MPAA are known to download films for the peer list. You'd still be on that.