Honestly, I think the tradition of the supremacy of the captain, the responsibilities of the officers, and the formal chain of command has more to do with the military origin of merchant shipping than any intrinsic sociological characteristic of the sea. The legal momentum of the accountability of the captain is substantial. But I think some recreational boaters are surprised to discover that the helmsman is typically legally accountable in most simple recreational cases, giving the supremacy of the captain pretty much no legal basis.
For a smallish sailing yacht, as a practical matter, whoever is on the helm is going to be in charge. It's not clear to me that militarizing the yachting context is any more necessary than, say, militarizing the automobile context. You don't need a captain and chain of command to drive down the freeway; you just need the driver to drive responsibly, and slow down or safely park the car if something comes up that they can't handle.