Well, about 2000 chinese noodle chefs were replaced by robot noodle chefs for the same reason robots are used everywhere.
Robots were less expensive (even than chinese noodle chefs), could work double shifts every day, 7 days a week and on holidays. When sick, they could be replaced the same day with a new one. The robots were more accurate, made less mistakes, had no legal liablity (no cut fingers, etc.) and the investors got to keep more money.
It's the end game that doesn't work. When 25% of the population can't get work because anything they can do can be done better, cheaper, and longer by a robot (or automated process -- i.e. computerized receptionists) then the system breaks down.
By definition, half the people are less than average intelligence. And many high intelligence jobs are being and will be automated as well.
The return is enormous (replace one or more highly paid humans with a machine or program) so the incentive is high.
The robot designer above is an excellent example. Sure- she'll continue to have work. But that's 1 job created for 1,000 jobs destroyed.
When people can't trade their labor for value/goods/housing/food what do you think is going to happen?