Of course, if they were breaking rocks with twelve pound hammers cheaper than rock could be produced in a rock-crusher, and somebody came along and said, "Take our jobs."
The response would be, "What's the point?"
But that is not what they were doing.
I believe you have said before that machines could harvest the crops as well as and cheaper than people can but in many cases that is not true. In some cases where it is true it is still not automatically desirable. Tomatoes can be harvested mechanically. In order to do this and still get something on the shelves that people will buy a type of tomato had to be developed that could withstand the rigors. They are notoriously tasteless.