Eh, I feel like if the school isn't explicitly asking, "why us?", then they don't want to hear it. There are only a few template questions, about challenges, diversity, "why us?", etc. If they're not including a template question, my guess is its not important to them, and they recognize that they're a top tier medical school that excels in basically every clinical field, and so me mentioning some niche program they have to show I read their website doesn't mean much.You're right, but you can say that for absolutely anything at all that anyone would write!
The simple fact is, every school doesn't feel the need to put every conceivable prompt in their secondary, and the free form "Anything Else?" prompt is meant to be whatever you want it to be, so that you later cannot complain that they didn't give you a chance to place something you feel is important in front of them.
But mostly I was just interested in what other people are doing. Are you writing a "why us?" response there?