W is for Wardroids

Near the end of the Great Interplanetary War, all was but lost for the allies. That is until robotics genius Maximus Bauernhof created the wardroids. These efficient soldier drones soon went into mass production and were sent to Earth in large numbers, decimating the planet and its inhabitants. They won us the war.

During peace time we had little use for the thousands of wardroids stored in warehouses all over the solar system, and so they were reprogrammed as cheap servants.  As an added bonus, they were also given female bodies and basic personalities so they could service more primal needs.