I think that as much as it’s important to know whether an object has a modifier, materials etc., the same logic should apply for physics. Even if for objects physics are listed also as modifiers, I think it would be more intuitive to specify it, and in the case of force fields it would be more for consistency, considering that they don’t have modifiers and they have no data icon in the outliner to facilitate recognizing them.
I’m asking this also considering the future, and wonderful, implementation of Outliner/properties syncing.