Sometimes, I get started writing an answer and have to leave for a variety of reasons. Later on, I come back and revisit the question, and still want to answer it. But the fact that I had invested so much time (OK, several minutes isn't that much...) and would have to redo the work is demotivating. I rarely rewrite my answer and complete it. Instead, I just go on to a different question.
If Bright Journey could keep my partially written answer as a draft, and retrieve it the next time I visit a question, I'm certain I'd complete a lot more of these.