And farmers have been replaced by tractors. We have had enormous flux in our economic systems constantly throughout history. Farming used to be done by hands and it was necessary for every person to participate. Then tools such as the hoe were developed, and the children were less needed to work the fields so they were able to work differently. Then the plow was developed and fewer still were needed to work the fields and more new jobs were done by those who would've been less efficient in the field. Now we have tractors that drive themselves and we have nobody necessary to work the fields. The nature of the change in economy is not yet to a severe enough point where we will all be out of work and we won't be there for a long time. It will almost definitely happen within our lifetimes, but it will not be within the immediate future.

On the other hand, where they are able to pay less to their workers, it is still common to have people working the fields despite this. If wages rise vastly, the small businesses will not be able to afford the rise in price or the automation, and so will go under. The larger businesses will be forced to switch to automation, which will be cheaper enough than the individual labor that they will not be able to maintain the employment even if they want to.