oddly enough star wars extended universe has delved into this topic. in core worlds, droids are easy to come by and obtain replacement parts and perform regular maintenance, hence droids are more popular than slaves, the cheapest of labour in the galaxy. Conversely in the outer rim where droid parts are expensive if you can even obtain parts, let alone regular maintenance cycles, slaves are cheaper to feed, house, and maintain their numbers than it would be to keep a squad of droids up and running. the translation to real world is big cities would be viable for machines like this, rural areas would not, depending on travel times and shipping speeds. Alaska might be the best example of an outer rim territory, while new york would be a decent example of a core world, with easy access to parts and service centres for regular maintenance.