Capitalism requires a strong consumer base to buy the products produced by capitalists. As robots take over more work in more industries companies fire more employees, eroding the financial strength of the consumer base and decreasing sales. Each company will keep trying to increase its own profits this way with no regard for the economy as a whole. I don't know where this will end but there will be a lot of suffering and poverty along the way.

Under a socialist system, more robots should result in employees working less hours while receiving the same pay, maintaining their ability to contribute to the economy.