One very good reason can be seen today: after some of the books from the Sherlock Holmes series went into public domain, artists today are free to use and create derivative works based on&#x2F;off of them.<p>Case in point: &quot;Elementary&quot; [1] is a Sherlock Holmes series where both Moriarty and Watson are women, Sherlock Holmes lives in NY and he doesn&#x27;t get along with Inspector Lestrade.<p>If things never fall into public domain, doing something like this can be either very expensive (e.g. paying royalties) or plain impossible (e.g. the author simply doesn&#x27;t allow it).<p>Copyright laws were meant to incentivize authors to create more, but no amount of incentives will make Sir Arthur Conan Doyle create more interesting stories, about Sherlock Holmes or otherwise.<p>[1]: <a href="http:&#x2F;&#x2F;thetvdb.com&#x2F;?tab=series&amp;id=255316" rel="nofollow">http:&#x2F;&#x2F;thetvdb.com&#x2F;?tab=series&amp;id=255316</a>