Linked from
The 9 pages that link to Copyright Term, each with the reason it gives.
CopyrightRelated: The duration determines when exclusive control ends.
Public domainRelated: A work generally enters the public domain when its copyright term ends.
Copyright infringementRelated: Uses after protection expires cannot infringe the expired copyright.
Copyright lawRelated: The term marks when exclusive control ends.
Berne ConventionRelated: Berne generally sets a minimum term of the author’s life plus 50 years.