What makes it unethical? How is it different from advancements in technology taking away any other job, like elevator operators, numerous factory positions, calculators (the human kind), telephone operators, people who sew clothes (somewhat), and so on?

It seems to me that automating away jobs has historically bettered humanity. Why would we want a job to be done by a person when we can have a machine do it (assuming a machine does equal or better)? We can better focus people on other jobs and eventually, hopefully, with no mandatory need for a job at all.