Peds floors are cool - they smell clean, they're bright, cheery, fun, and you get the sense that the kids won't die (or this is your subconscious convincing you of this). The children generally are outgoing and curious, even while in the hospital.
Geriatric floors smell like GI bleeds, cancer, dehydration. They're full of older folks with alzheimers screaming 'HELP ME! HELP ME!', moaning constantly, depressingly quiet at times, and you just know these people will die soon. Not the kind of place to take people who are thinking of medical school. Think of it - you have a choice of taking them a nice place with sick people that will likely get better or a place that smells like vomit and GI bleed and looks like a dark place where people go to die. The older folks generally want to be left alone, they don't want to see ANYONE, including their doctor and you.
If you were in the admissions department or leading the tour, which place would you rather go?