I've seen all these complaints for the product owner/manager doing nothing and maybe I have different experiences, but the one in my team seems to say least somewhat keep up with what the business wants and what the developers can accomplish. Albeit still just a middle manager that doesn't do much actual work. The scrum master on the other hand does literally nothing but pretend to act as a bad babysitter for the team and doesn't provide anything. Can't truly grasp what he gets paid for other than having a scrum master certificate (presumably writing his name in crayon on it).