Causes
According to Neil Netanel the increase in orphan works is the result of two factors: (1) that copyright terms have been lengthened, and (2) that copyright is automatically conferred without registration or renewal. Currently only a fraction of old copyrighted works is available to the public. Netanel argues that copyright owners have "no incentive to maintain a work in circulation" or otherwise make their out-of-print content available unless they can hope to earn more money doing so than by producing new works or engaging in more lucrative activities.
Read more about this topic: Orphan Works