Ignorance? Not at all. YC has thousands of applications to read in a short period of time. If a question says "If you're already incorporated, when were you?"

Ignorance? Not at all. YC has thousands of applications to read in a short period of time. If a question says "If you're already incorporated, when were you?" and I go on to explain why I'm not incorporated, I'm wasting their time. N/A means "I'm not incorporated, this does not apply to me." Go and read the questions that have N/A as answers. They simply do not apply.