Question is then, why do you have both? Where does this implicit "hierarchy" come from? It is simple: As soon as you have multiple people working on a problem there are communication requirements. You can organize things in a way that they support these requirements or you can just let them figure out how to adapt their needs around some existing hierarchy. Now which one do you think is more efficient?

Hierarchies are just an organizational pattern, a tool. There are neither a religion or "set in stone" as many think, they create communication choke points, induce unnecessary communication, cause "not our responsibility" mentality that may result in things falling through the cracks, have often the "Chinese whispers" problem to it, and so on. You cannot treat every problem like a nail just because your only tool is a hammer.