> Do a plumber, a baker, a policeman need a computer to do their job?
Plumbers (and for that matter, all tradespeople) can get far more efficient at their jobs if they use computers to their advantage. Modern heating systems, i.e. anything above "a gas boiler that circulates water and fires up if the water gets < 70 °C and shuts off >90 °C" can't be designed these days any more without the aid of simulation software that accounts for the effects of insulation or the variety of air-conditioning systems. The more energy efficient, the more complex it gets to design and to operate. Carpenters these days don't do much measurement by hand - they design something in CAD and get exactly fitting wood parts out of their saw machines. Electricians, where do I even start with these, as modern homes are filled to the brim with smart tech. The only thing AI can't do for now is actually run cables and pipes, but give it 10-20 years and construction labor will be done by Boston Dynamic robots - we're already seeing giant 3D printers for concrete or brick-laying robots.
Bakers just the same. Most of bakery, with the exception of artisanal crafters that take pride and charge appropriate pricing, is automated these days - including the supply chain. There aren't that many humans involved in the production of staple foods any more, this is why everything has gotten so cheap and plentiful over the last decades. Some stuff, like picking asparagus, can't be done by robots yet, but that's bound to change.
And policemen... just look how much they're using computers already. No more "send a chopper and a dozen cars to follow a suspect", no more stakeouts, ANPR cameras and AI are enough (there's been a HN submission a week-ish ago about that).
Yes, all of these jobs can be done by computers, but far far less efficiently - and declining birth rates will put more and more pressure on all kinds of jobs to be either eliminated entirely ("paper pushers" and similar bullshit jobs) or be replaced by computers.