Undergraduate Admissions at UW-Madison: Application statements tip sheet Write on Both Topics: There are two statements. Write on both. Those who do not are less likely to be admitted.
It can't hurt you to answer the second one, so why not? According to that link though, yes, it will hurt you to not answer it. You
always have something to share, you just might have to think about it.
Is it possible to not answer it and get in? Yeah, of course. I didn't answer it, my friend didn't answer it, and we got in, and I'll bet many others had the same situation. I think it's slightly risky to not answer it, especially if you think you'd be on the edge of admittance, and I know I regretted not answering it after I submitted my application.
So my suggestion is to go for it. Like it said, it's not just to explain a bad grade/semester, your test scores, etc. Think about it for a while. I'm certain you'll find something to write about.