The answer to the question Jesus poses here is obvious. Of course, the owner will not invite his slave (the best translation of the Greek word doulos), after he finished his work on the land, to his table. He will surely not do that. The social relationships then did not allow for this.
7 Qui de vous, ayant un serviteur qui laboure ou paît les troupeaux, lui dira, quand il revient des champs: Approche vite, et mets-toi à table?