Anti-Piracy
Anti-Piracy is the the reason that copyright extremists, such as the MPAA or RIAA, cite as the purpose for implementation of DRM technologies. In fact, all DRM systems are inherently flawed and do not prevent piracy of digital content.
The true purpose of DRM systems is often to create artificial market segmentation (as in the case of DVD region coding) or to create artificial barriers to entry for competition (as in the use of Apple's FairPlay DRM to prevent non-Apple players playing song bought from the iTunes Music Store).