Ideas, vision, and channeling them into prints. There's a lot of things going on before the negative is even exposed, let alone developed, and ultimately printed. All those ideas of what the pictures should look like are infinitely more important than any material. As you say, it's about finding something that stops being an obstacle in the creative process, that makes it easy for the ideas to materialize.
I like how clearly you think, and how good you are at eliminating BS, Massimo.