Finally watched Brave last night and realized that Merida is the most recent Disney "princess" to be shown barefoot. Snow White, Cinderella, Aurora, Wendy, (is Alice shown barefoot? She's not a princess but she's an animated Disney leading lady), Maid Marian, Eilonwy, Ariel, Jasmine, Pocahontas, Esmerelda, Jane, Mulan, Megara, Lilo, Kida, Tiana, Rapunzel and now Merida. Belle is the only one who isn't.
Each one is shown barefoot in relation to being either lower-class (Snow White, Cinderella, Aurora, Tiana, Jane, Esmerelda, Lilo, Mulan Pocahontas, Ariel, etc.) and/or ass-kicking (Maid Marian, Eilonwy, Jasmine, Megara, Kida, Rapunzel, Merida). To be shown barefoot generally, though, is a sign of vulnerability - Wendy is the only one who emphasizes this. Some would even call it sexual.
It just seems strange to me that there would be this trend. Whether it's to make the animation more simple or more creative, I couldn't say. I'm just curious as to why, and why Belle (and Alice?) are the only ones who aren't shown barefoot.