While child labor is viewed negatively, apparently child labor and child slavery aren’t the same thing, and child labor though it could still be exploitative/cruel in other ways, can be done voluntarily by the child, and with fair treatment/compensation/etc.
I suppose you could make the argument that any child labor opens itself up to problems, but could it be done responsibly? And if not, then at what age do we draw the line of labor being not ok regardless of consent?
This is likely related to why kids can work in a family owned business to various extents. At least in the US. Not sure about elsewhere.
The problem is that once you make it available for anybody, it becomes a societal pressure and children won’t be given a choice since they can’t make their own decisions for what they do. Hell, how many of us were ‘forced’ to get a summer job as a teenager by our parents?