[Impossible]

You do it to understand the problem you're working on before you start writing production code. If you understand the problem you're working on, there's no need for prototyping, which is probably true for most code an average programmer writes. I tend to write prototype code to learn how something new works before writing production code, or when I have multiple ideas how a system should work and need to iterate on them and pick what I should actually ship. If you know you need to build a specific feature and how it should work you don't have to prototype it.