A healthy society needs to have means to support people of all intelligence levels, we need the equivalent of jobs for ditch diggers, and those jobs need to be respected lines of work for people.
Work has more value than just money, and whether people like it or not, it gives value and meaning to peoples lives. The value we assign (and pay) for work shouldnt just be governed by the economic value it generates, it needs to be enough to meet basic needs, to engender respect.
The basic point I'll make here, using ditch digging is - have you dug a ditch? I have, its hard work, and mine was just a small one in my back yard.