Managers can provide a useful role in setting the scene, reminding what the goals of the organisation, the department, and so forth are, and how this connects with what the team is doing. They are perhaps most useful in working with individuals who aren't working well as part of the team at the moment - giving them feedback, mentorship, building bridges, connecting them with people, training, and so forth.
In my opinion, managers hurt more than not if they override the self-organisation of teams, and this most hurts when you need two teams to work together - and one of the managers has (explicitly, perhaps) made it clear that doing things "off the plan" is not appreciated.
I'd agree at my startup employers. I would not agree about several teams I worked with at Apple, to pick on a corporate example. Teams built from the ashes of an acquired startup at Apple, again, I'd be more inclined to agree. You can't support a broad conclusion like that anecdotally, because I can counterexample it anecdotally, implying there's more to it.
It really depends on the ICs in question. Startups are far more selective about their ICs because one person has a very big impact. With the exception of Google and a couple others, large-cap corporate throws IC quantity at problems and distinguished, autonomous, "rockstar" (sigh) ICs are far more rare. You need the cat herders there.
You can't rely on any random grouping of people to decide well on what's important to do and how to effectively break up the work. But adding a random manager to that group doesn't help specifically. Adding a more experienced IC will generally help more than a less experienced manager.
To me, a complete highly motivated team (a team without any unmotivated person) would certainly feel like they should bring up some kind of organization. They are motivated, after all, and thus they want to get their work done.
A not motivated person, however, needs to be pushed, not in a bad way, but in some way, because he/she is unmotivated (don't feel like wanting to get any job done), and thus the hierarchy comes into play.
Most people fall in this "unmotivated" category. And that is (I think) the actual true reason why management exists in the real world: to push (unmotivated) people, so they get their work done.
Note: by "push" I don't mean "being an idiot". I believe that the presence of the manager is already sufficient for most people to feel like they should work, even though they don't want to.