I personally use the application as a way to test out my understanding and boiling down communication of ideas. I understand and have copied all the questions to a doc and use that regularly, but theres something about filling out the application on YC that makes it different.
If you allowed founders to use this application as a sandbox for all their ideas, this data would be insanely valuable. Seeing multiple draft applications from someone would give indicators about thought process and more importantly progression. Not to mention a wider understanding of markets that entrepreneurs are thinking about.
Product of not being able to fill out the application for a side project, headed back to github.