Show me an actual person whose livelihood or retirement depends on their copyright (and not, say, owning somebody else's copyright). I'm not convinced that the current state of copyright law actually benefits authors and artists.

Nearly all fiction authors own the copyrights to their books. They have an agreement with publisher to publish it and they get the royalties. If that agreement ends, they can find a new publishers. The authors get an advance and if book is popular enough, they get royalties.

Any semi-famous author would do, no? Famous authors everyone's heard of are probably rich enough that they have other investments via money they earned from their copyrights, but arguably that's still a living derived from their owning of copyright. So let's start with hearing why, say, Stephen King, Charlie Stross, and J. K. Rowling aren't actual people who's living (sizable as it may be) doesn't depend on their copyright on the books they wrote, before we look for any lesser known authors. Taylor Swift makes a living off her music, which is dependent on copyright. Or have I missed something somewhere?

Okay so say I write a book. And I go to a publisher and show them the book I wrote.

What is the name of the law that prevents the publisher from kicking me out of the building, printing the book I wrote, and making money off it?