I suspect it's because the farmer wants to finish the milking before dinnertime, and it needs to happen at least twice a day. So 4 AM+4 PM works out according

I suspect it's because the farmer wants to finish the milking before dinnertime, and it needs to happen at least twice a day. So 4 AM+4 PM works out according to the farmer's schedule. Automated milking machines are available on demand, and I am not aware of there being a "cow rush hour" on those, with annoyed cows queueing to use it at the same time, and telling each other to hurry up. They just step up as they require and let the robot handle it.