If we build AGI, we don't have a past comparison for that. Technologies so far have always replaced a subset of what humans currently do, not everything at once.
Nineteen Eighty-Four would like to have a word with you!
Out of all SF, I would probably want to live in The Culture (Iain M. Banks). In these books, people basically focus on their interests as all their needs are met by The Minds. The Minds (basically AIs) find humans infinity fascinating - I assume because they were designed that way.
It’s a good thing to keep in mind that plumbers are a thing, my personal take is if you automated all the knowledge work then physical/robot automation would swiftly follow for the blue-collar jobs: robots are software-limited right now, and as Baumol’s Cost Disease sets in, physical labor would become more expensive so there would be increased incentive to solve the remaining hardware limitations.
Here’s a napkin-sketch proof: for many decades we have had hardware that is capable of dextrously automating specific tasks (eg car manufacture) but the limitation is the control loop; you have to hire a specialist to write g-code or whatever, it’s difficult to adapt to hardware variance (slop, wear, etc) let alone adjust the task to new requirements.
If you look at the current “robot butler” hardware startups they are working on: 1) making hardware affordable, 2) inventing the required software.
Nothing in my post suggested costs go to zero. In the AGI scenario you assume software costs halve every N years, which means more software is written, and timelines for valuable projects get dramatically compressed.
It would not even necessarily result in a human-like robot - just some device that can move the water heater around and assist with the process of disconnecting the old one and installing the new one.
If AI kills the middle and transitional roles i anticipate anarchy.
Especially with essentially unlimited AGI robotics engineers to work on the problem?
Also don't forget that plenty of knowledge work is focused on automating manual labor. If AGI is a thing, it will eventually be used to also outcompete us on physical work too.
People like to point to plumbers as an example of a safe(r) job, and it is. But automating plumbing tasks is most difficult because the entire industry is designed to be installed by humans. Without that constraint it would likely be much easier to design plumbing systems and robots to install and maintain them more efficiently than what we have today with human-optimized plumbing.