I think it varies from company to company. I worked in highly corporate environments where the scrum master had tons of work to do and took a considerable load off the rest of the team. Having said that I saw them more as delivery leads, which we did actually call them. They also acted as team managers but only on a project level, not people management level. It was a funky role, but they really did a good job.

Where I am now, it's less corporate, and there is no scrum master, but rather the team manager deals with the various aspects of agile, but they're also people managers, so again, different.