" But just think of how many clever inventions are essentially labour-saving devices, at all levels of technology."
I knew you were , and I understand that you are, defining "technology" mostly from the perspective of the "consumer "
and products mass produced for your convinience . You're reference to the purely commercial term "labor saving devices" confirms this. But this is a miscomception as these home-use contraptions are but one small portion of what has been the technolosphere.
That is why , for example , I intentionally mentioned the technology of ocean sailing ships of which the U.K. built its empire upon. Not to mention the mass production mechannics of the Industrial Age. Any student of Charles Dickens would wonder out loud where some get the "quaint" notion that this was meant as "labor saving" ( least of all *child labor*-saving ).
The railrodas were hardly labor saving , but labor multipliers as in moving more freight faster than horse drawn wagons or canals barges . Do you then believe that canal transport traffic was more labor intensive thus causing the creation of so-called "labor-saving" locomotives? ( How many folk songs written about the hard life of the railroad wage-slaver need one be reminded of ).
Most technology is designed for evermore levels of concentration of power; natural, corporate, and political and "saving labor" is but a colateral effect when convinient of profitable.
Man ,this is supposed to elementary-level history for anyone who knows their the British Pre-Indistrial to Post-Industrial Age.