The use and loss of personal power.

[The Squatter of Amon Rûdh]

That's a good story.

The dispersal of power is an interesting and probable side-effect, but I think that the intention in making Two Trees, the One Ring, the Silmarils and the ships of Alqualonde into once-only creations was to emphasise their value and to make certain narrative situations work properly: the destruction of the Two Trees is a lesser tragedy if two more can be grown in their place; if the ships of Alqualonde could be replaced there might have been no kinslaying and so on.
I think (wholly without factual evidence) that the idea that some things are irreplacable, but that we should never let that lead to rash actions, was an important one to Tolkien.