Not quite true: when we're all living in modular robot houses that aren't human-maintainable, the plumber's got no purpose anymore. But for the time being, he's

Not quite true: when we're all living in modular robot houses that aren't human-maintainable, the plumber's got no purpose anymore. But for the time being, he's got a very large installed base of stuff to maintain, and he's going to be as secure as he wants to be (if he knows enough of the entrepreneurial thing to manage a personal business and his reputation).