I'm not a laywer, but I think the concern with protecting trademarks is to demonstrate that you actually have an interest in said trademark, and are not simply

I'm not a laywer, but I think the concern with protecting trademarks is to demonstrate that you actually have an interest in said trademark, and are not simply trolling your competitor. By having a token royalty, they demonstrate that they do care about the trademark even when it is being used by someone they would otherwise like to hurt.