Fundamentally, copyright is the government promising to beat up anyone that copies a protected work. Now, we don't live in a complete dystopia, so it's not lite

Fundamentally, copyright is the government promising to beat up anyone that copies a protected work. Now, we don't live in a complete dystopia, so it's not literal beatings. It's legal protection and the beating up is the infringer of the copyright having to pay a bunch of money to the copyright holder. That means that the government is spending resources in order to maintain that copyright. Government is funded by "the people", and so "the people" are paying to beat up anyone who sells a Mickey Mouse doll. In actuality, the reason it doesn't work like you'd expect is because "the people" are separate from "the government", and it doesn't actually cost much to maintain copyright. But there are a bunch of interested parties in getting to keep monopolies on copying for long periods of time. But yeah, the reason they shouldn't last forever is because they are relatively expensive to maintain, and some great works can come from public domain stories (case in point, the lovable Mouse who used Grimm's fairy tales as the basis for all of it's most profitable works). Life of author? Definitely. But if the author assigns rights to a corporation? Probably shouldn't allow it to extend 200 years or whatever Disney is up to. Disney won't die, so there is no natural end to the monopoly, and Disney has also proven that they aren't interested in branching out to new stories (perhaps because us humans like the old ones so much). A reasonable copyright in a digital age is probably something like life of the author, or 25 years after transfer to a corporation. This still effectively provides 75+ years of protection for most works, but then the author gets more say (because transfer of ownership can't happen without giving up monopoly rights sooner), and things like film and games and such aren't locked up for hundreds of years, as it would be surprising to have them owned by a human.