A lot of superheroes tire after using their powers too long. Also, I have superior intelligence to that of a majority of the world population. Building robot servants is too risky. I have built robots before and the amount of data required for a robot to actually respond to human commands and function as a human would is nearly impossible. There would need to be a mass of computers too large to have in a house to supply the amount of data to make a robot function like Iron Man's legion.