Going off some of the rumors, I assumed part of it was simply to satisfy their Eppy-like egos - not only do they feel superior to normal humans because of the Cardamine, they treat normal humans as property to be bought, sold, and worked to death.
That and, as has been said, components are not a complete robot.
Robotic components are just parts for Robots, as stated by the info card.
Quote:ROBOTIC COMPONENTS
As the use of robots in industry became more and more widespread, it became necessary for robotics manufacturers to standardize the replacement components that frequently wore out or were damaged. Robotic Components include a wide variety of gyros, stabilizers, sensors, manual manipulators, and other components that are frequently replaced. The increasing use of robots has also contributed to unemployment among various industrial and agricultural worker groups, leading them to target the transport of Robotic Components as part of their terroristic campaigns against their former employers.
So, Robotic components are used to repair robots, not build them.