because it never influenced it in the first place.
Except that Michael Jackson was influenced by Little Richard, James Brown, and Diana Ross. And Michelangelo lifted Ghiberti's Gates of Paradise for the posing of the Sistine Chapel. And every artist ever is influenced tremendously by all the artists that preceded them, and no art is created ex nihilo. The arguments for not releasing an artist's work (ie copyright) are never that the artist doesn't owe anything to society, but that the artist needs to make a living, or to ensure that their children are provided for.
In other words, yes, society really is entitled to everything a person creates, ever, even if they never published it, because that person appropriated the majority of their work from society in the first place. Our societies have, in the last 400 years, been willing to trade some of what we're owed in free speech in order to provide monetary reward to the artists, but we're still owed that speech. Disney didn't invent Cinderella, Dan Brown didn't invent the Catholic church, Dan Bull didn't invent either rapping or Skyrim (nor did Bioware invent fantasy adventure or videogames, nor did Tolkien invent magic rings or elves, etc.., etc., etc.).