You're looking at the wrong part of the chart, I think. If there's nothing on the market from the '60s, say, then those writers are getting absolutely nothing for their troubles. They get no money from licensed products and no exposure from unlicensed products. At best, they get to play trolls under the bridge, hoping someone steals their plot so their lawyers can soak both the offender and them on a lawsuit.
You could also make an argument that the fact that something is in circulation is a sales figure. In a remotely healthy economy, companies don't waste much time reprinting books nobody wants to read. His numbers aren't coming from e-books, after all, where the investment is low.