Let me try to be more concrete. Competent writers, generally, know that they should avoid using two words when one will do—to take one of the most basic writing tips. They can also articulate this knowledge—although it's far from self-executing, begging the question, after all, of when one word, in fact, "will do." That knowledge is mostly implicit.

Yet, it's impossible, or nearly so, to write competently without being able to articulate this rule, which doesn't emerge spontaneously from comparing good and bad writing, but rather helps define what makes writing good. Conciseness as a goal is part of understanding writing's function. Some writers might figure it out for themselves, but however they get it, they're going to have to get it in an articulate form. Prolixity is inherently pleasurable, so lean writing demands discipline. And the enforcement of discipline is the role of the conscious, articulate mind.