What's the motivation for replacing humans in various jobs with a robot?
To cut costs and/or improve quality.
The outcome is going to be terrible
Possibly. Then again, maybe not -- you've seen what the open Internet did for information (which is now easily available to most people at very low cost); perhaps robotics can do the same for goods and services.
"But what about all those people who will lose their menial jobs", you ask? They'll have to find some other way to make a living, is the answer. But with manufactured goods and services practically making themselves, that shouldn't be so difficult to do -- if nothing else, the government could put a tax on automation and use a portion of the wealth they generate to provide every citizen with a guaranteed stipend. People would then have time to learn more advanced skills that would make them employable again, or they could just become (effectively) retirees, and do things they enjoy rather than do menial work most of their lives. Either way, they wouldn't starve.
Of course that will require some political will, but that doesn't mean it can't happen. Our society has absorbed changes of similar magnitude before, it can probably do so again.