Copyright was hatched back when the act of copying was laborious and mechanical, meaning that the copier likely had deep pockets and financial backing (and there were few of them in the neighborhood).

This logic falls flat when we get a device that is basically built for copying, the computer. A major part of how it operates is to copy data in and out of memory.

Anyways, even before the computer various nations had exceptions in place for copying between friends and relatives. This because even policing the likes of cassette based copying was virtually impossible without a permanent copyright cop in every home.

These days however said copyright cop is being implemented in the form of DRM and the kind of content fingerprinting talked about in the article.