Because it's illegal to pay so little, and nobody would do it for that price anyway, except for maybe your own children, who do it for that price plus the negative incidence of an asswhooping. If it were affordable for common people to have servants or slaves, they totally would. Machinery priced slaves out of existence. The next frontier is for value-added centralized industrial manufacturing to be priced out by distributed manufacturing and recycling, not a return to the days of domestic servitude.