[thaumasiotes]

> Fire [...] can lead to writing tens of thousands of years down the road (papyrus happens to preserve well in a pyramid in the desert, but cooking clay tablets or melting metals works better everywhere else).

I feel pretty safe in saying fire had no direct influence on the development of writing anywhere. Chinese characters first show up carved into bones. (They are well-developed at this point; obviously they originated some other way. But we don't know how.) Cuneiform tablets were originally unbaked; baking for preservation was an innovation that happened long, long after writing was established.

And the difficulty of working with metal means it is totally unsuitable as a writing medium. Although particularly important cuneiform documents (peace treaties) were sometimes cast in metal, only the final draft would be -- as the treaty was "in negotiations", messages back and forth were in clay. A society that can only write on metal is a society that will never develop writing in the first place. There is no reason other than wishing to impart a ceremonial permanence to write in metal.