I didn't make any of this stuff up, people who think about these things know all about it. Still, photographers seem to be really in to copyright, and often a bit clueless about it.
This isn't a reference on copyright law. For that I suggest that you just go and read the law, it's surprisingly readable. There are also umpty-million web sites with loads of information, some of it correct.
This is a post about copyright, and its lifespan. Copyright is the right to make copies, and copyright law is about regulating who has that right, in what forms, and what it all means. Copyright law makes no sense for things which cannot be copied. Just as there are very few laws regulating the use of magic, there was little to no copyright law before the invention of the printing press. Copyright law also ceases to make sense when the ability to make copies is completely ubiquitous. You can have all the laws you want, but they're un-enforceable.
Copyright as we construe it makes sense, roughly, from the period between the invention of the printing press and the invention of digital media and digital networks.
This isn't a question of what is right or wrong. I create intellectual property for a living, I am certainly not advocating for the destruction of intellectual property rights, I am facing the reality in which we live. Digital media and digital networks are in the process of rendering large swathes of intellectual property rights completely moot. A king can claim the newly discovered continent of North America all he wants, but if he can't enforce that claim it might as well not exist.
There are serious questions confronting us. We don't actually know what to replace copyright law with, if anything. We don't actually know if capitalism can survive the advent of digital media. We don't actually know if civilization can. We've never tried it before.
It's exciting, isn't it?