Even for slavery - we can easily argue that free housing and food would be a huge boon for a lot of people. Imagine how many homeless people can quit drugs and have a roof over their head if we just allowed them to work for just housing and food. We'd create practically infinite jobs.

But we choose not to do that because that's bad.

There's people out there desperate enough for anything. Anything. There are people who would happily sell their limbs.

The argument of "well it helps them and they want it" isn't very good. That's not how we operate generally - we need something more than that.