“Mostly it’s human sweat and toil, though. This sort of thing is hard to properly automate, while humans are good at adjusting and adapting on the job. That’s part of it. More than that, though, it’s expensive to automate, and would require a highly trained crew of valuable technicians and operators running your fleet of shiny machines. Because once you invest in automation, you have to take care of your junk. With labourer-class people, not so much. It’s cheaper to have a half-assed crew of expendables that you know you’re never going to have to return in good condition or risk losing your deposit. Earth has a lot of surplus people”