I can think of arguments why derivatives should get more favorable and less favorable treatment than overall copying. To me it feels like a wash and they should probably be treated similarly-- though trademark can provide some limited protection beyond copyright terms if the work's use in commerce has been continuous.
The original thing has already been created, and proceeds benefit whoever created it (or who they sold rights to).
Whether they choose to continue to actively market it or not, while under copyright, can't be influenced by copyright. Abandonware under copyright is still abandonware.
But! There's a class of derivative works, built on top of the original, that currently can't get made.
If they were, we'd all be better off.
Arguably, I can even see an aggressive sunsetting for derivative works being net positive for the original work's commercial value ("See the original").
I can think of arguments why derivatives should get more favorable and less favorable treatment than overall copying. To me it feels like a wash and they should probably be treated similarly-- though trademark can provide some limited protection beyond copyright terms if the work's use in commerce has been continuous.