The way I see it, that's what a developer is: a tool for translating fuzzy requirements into rigid definitions. Sometimes they're just plain lazy about that task, but even when it's done well, they discover vagueness and incompleteness in the specifications. They use their judgment to fill that in, but they're often wrong, especially when they don't really know the domain.

Programmers want rigid requirements, because that makes their job easier. Indeed, it does their real job for them. If we had a really rigid way of writing specs, you'd just write a compiler for it. The real job of a programmer is precisely about playing intermediary between the true rigor of the computer and the pseudo-rigor of requirements.