Why post a write-up?

What's a main reason you post a write-up on E2?

The betterment of Everything.
It's a subject I knew nothing about and I wanted to research it.
It's a subject I know something about and it wasn't noded/noded well.
To make people think.
I did it for homework and had it around.
I was inspired by a node title/nodeshell.
I didn't agree with the write-ups that were there.
Actually, I have no reason to post write-ups, so I don't.