For one thing, there is all of the material getting removed by streaming services either for controversial content or simply because it is no longer profitable for the services to host them.
My plex server is probably 90% things that are over 10 years old. I relatively recently finished Columbo. I don't really have much of a problem pirating something where most of the people who were involved are dead or in a nursing home.
I ask this without irony: is there even anything worth sourcing from the high seas these days? Entertainment has largely turned to crap in my opinion.