Maybe some civilisations are techno-phobic? Or maybe slaves are better than robots for some jobs.
Michael
This^ and slaves are a lot more exclusive than robots. You can choose between a robot vacuum cleaner or a maid? what do you choose?
Robot vacuum cleaner vacuum clean period!
Maid can Vacuum clean
Maid can make drinks
Maid can iron your shirts
Maid can make your tea
maid can....[fill in blanks]