Once robots start flipping burgers and they can get rid of all that expensive labor ...Will there be enough useless eaters around for it to be profitable to sell them hamburgers?
You just hit upon the reason corporations are in favor of progressive policies like welfare. They sell products to food stamp and welfare recipients. Those recipients get government money to pay for the products. Corporations also sell to government agencies at all levels. Corporations support progressive programs that spend money to solve problems, like data processing, office supplies, and weapons.
The government gets the money from future taxpayers. As long as there is a future with taxpayers who haven’t been born yet the government will be able to borrow money. Why do we have a national debt of over 20 trillion dollars?