Human culture isn't designed intentionally by anyone. Human culture is emergent, and is built continuously by everyone through the constant feedback loop of interaction with other people, individual experience, and social learning. No one is designing it from the top down.
It is a mistake to assume that any aspect of human culture is "for" anything in the narrow sense. Certainly culture emerges out of a historical process which can often be traced, and certainly there is the broad sense of "purpose" in which an aspect of culture might be perpetuated because it benefits certain people in certain ways, etc., but this is all an unplanned, decentralized, non-directed process. There have been efforts in human history by powerful institutions—like states—to shape culture in particular ways, and sometimes they see some amount of success, but the vast, vast majority culture is not produced in this way.
There's a particular post I'm vaguing here, whose political orientation I don't even particularly disagree with, but it significantly rubbed me the wrong way because it was worded as if culture was basically something engineered from the top down, in which everything has a discernible, coherent "purpose" that can be logically deduced. No! I don't think that's actually true!
