The core motivating idea [for limiting copyright terms] was the restriction of monopoly. The English, of course, had learned to hate monopolies; they had essentially fought a war over Crown granted monopolies. As the United States Supreme Court decided in one of its really good intellectual property decisions, the Statute of Anne was written against the backdrop of practices –eventually curtailed by the Statute of Monopolies – of the Crown in granting monopolies to court favourites in goods or businesses which had long before been enjoyed by the public. For example, the printing of the Bible is a monopoly granted by the Crown. Writs of Courts of Common Pleas were a monopoly controlled by and rented by the Crown. Clay pipes were granted monopoly control, gold and silver thread and most famously, of course, playing cards. This tradition of granting monopolies over stuff that already existed created the ire in the British people that led to a revolution against these monopolies. These monopolies for existing things were the product of an endless lobbying by those who produced those existing things, lobbying to protect their monopoly.
Open Content Licensing: Cultivating the Creative Commons