They do have reasons to be slaves, so I have been considering this alternative too, where they only accept being freed after they have become comfortable with the protagonist (as it happens for both characters, if you are on the "right" path with them). Acknowledging it is important, since freeing them is one of those options which make sense. Even in the game's world, slavery is a rare thing, with specific laws and rules (when done legally), so it would be weird to not give the option, even if it's symbolic with no actual gameplay changes.