That's been the 'endgame' of technology improvements since the industrial revolution - there are many industries that mechanized, replaced nearly their entire human workforce, and were never terribly profitable. Consider farming - in developed countries, they really did replace like 98% of the workforce with machines. For every farm that did so, so did all of their competitors, and the increased productivity caused the price of their crops to fall. Cheap food for everyone, but no windfall for farmers.

If machines can easily replace all of your workers, that means other people's machines can also replace your workers.