I do this "job." I manage managers. Most of the time, your sentiment is entirely correct — we're useless. We don't have to be, though.
My previous boss made it his life mission to find every bit of pointless, time wasting nonsense that came from above and shield us from it so we could do our actual jobs. A lot of people didn't realize he was doing it until he was promoted and left.
I spend most of my time finding ways to automate away boring things my employees do manually, so they can spend more time on the interesting parts of their jobs. I also spend a lot of time finding and getting funds for development and training they want so they can grow their careers. The rest of it is spent advocating for resources to the people that control them, hiring new people, and explaining what my people do to folks who are probably too dumb to understand it.
Your boss is probably useless. Most of us are. If you ever find yourself taking his place, remember how useless he was and how the value in your office is generated by the people who make things, not the people who "manage" them.