"The way this casual remark is made seems to indicate that robots are a reality."


It seems that Vance doesn't forbid the existence of robots, he just doesn't use them in any significant way in his stories. He has said somewhere that robots can be written to do anything, which he sees as a kind of cheat, literally a deus ex machina. So he writes stories about humans interacting with other humans (and the occasional deodand, demon, or vegetarian).