Secondly, and more importantly, depending on human workers is problematic. They get sick, they strike, they complain, they miss work or show up with a hangover and are generally unreliable when it comes to keeping up quality. Machines and robots can break down, but are on average far more dependable and reliable. So switching to machines or industrial robots gives great advantages to producers.
The economics of machine labor are generally predicated on inherently imbalanced economic analyses, which stem from poorly-conceived public policy. Human beings are forced by the state to pay for social responsibility. They pay FICA tax, income tax, sales tax, property tax, gasoline excise, etc. These taxes provide insurance for people who can't/won't save for retirement, take care of their health, or maintain employment. We also have socialized cost structure for infrastructure, monetary system, judicial system, and defense. Machines benefit from our infrastructure, monetary system, judicial system, and defense, but they pay no tax. Furthermore, every dollar we waste in the social system, further degrades the plight of lower-middle class laborers.
What you realize is that the master welder lost his job to a robot because the company didn't have to pay direct/indirect taxes or mandates on behalf of the robot. If robot productivity were taxed (not beneficial for anyone) or if the government provided a refundable tax credit to offset onerous regulation costs for the lower-classes, the economics of automation would not skew heavily towards machines.
