The primary method of milking cows in the US has been by machine for decades... And most farms in the US are highly automated: automated sprinklers, automated

The primary method of milking cows in the US has been by machine for decades... And most farms in the US are highly automated: automated sprinklers, automated tractors, automated planters, automated harvesters (of crops that are amenable to machine harvesting). It's simply that there are a lot of food crops that are trivial for humans to harvest by hand that would require very expensive machinery and technology to accomplish with a machine.