I completely agree with your opinion that robot should replace human in the workplace. As you said for the first reason,  robots never stop working unless they brake down. At here, the different outcome about quantity and quality between human and robots is occurred. This is the big reason why we should replace robots in the workplace. However I disagree with your last reason that  our world can reduce the gap between the rich and the poor. If we replace robots in workplace, even if we do not want, there will be manpower replaced accordingly. On the other hand, there will be people who control and manage robots. So the replacement to robots have no choice but to have a problem about the gap between the rich and the poor.