[jchw]

Running teams is management. Not everyone wants to be doing the roles involved in managing teams, so it's a designated job title. If you get rid of the hierarchy entirely, then what happens is that they form implicitly and everyone is completely confused as to who leads what, and that only gets worse as teams grow and the number of projects grow.

Some management is bullshit, but literally "run teams" is the important part. But if you get big enough, you do wind up with departments. It grows like a fractal.