Should JK Rowling not have been receiving money from the first Harry Potter book (published in '97) for the last 6-11 years? Sure she's rich enough already... but why should she lose out on that money which she arguably earned?
And not everyone gets rich in the first few years after publication. My mother is an author of children's books, and my grandfather was a composer - money still comes in (not to me, to my mother and her sister) now, many years after some work was written, but it's never been a huge amount, even at time of publication, yet alone now.
I'm personally a fan of the (life + X) model, whereby it extends a little beyond the creator's death. I don't know what that X should be, though I do feel that the X=70years that we currently have in the UK is too long. But while the creator is alive, why should they not continue to earn money on their work?