The children yearn for the mines.
Trees and grass and other green things around you in the garden have a positive psychological effect. The feeling of having done something visible has a positive psychological effect. Getting a physical workout has a positive psychological effect.
I know yours is a humorous comment, but a child digging in a garden has nothing to do with them yearning to be an early-capitalism style child laborer.
Jesus dude, go touch some grass.
We all know it’s bad for children to work in mines, its a joke.