Librarians are extremely diligent about copyright and probably have a better understanding about it than you or I do. Of course, they don't have any control over what happens to media once it is in the hands of a borrower, but I highly doubt that it is a major source of piracy (for reasons mentioned above).

Oh wait! Are you confusing lending with piracy? They are entirely different concepts. Copyright only covers reproducing materials. Yet you are still free to lend out those materials as you please because you own the physical object. And if you are opposed to libraries lending materials you may as well oppose private lending between friends as well. That would make for a very selfish and very sucky world.