It might have been an evolutionary development because of the long skirts which constrained leg movement, but now it is perhaps vestigal because yeshiva girls with loose skirts yeshuffle as well. Many argue that is a combination of longs skirts and a defense mechanism to avoid goyim activities. Whether it is conscious or unconscious is still to be determined.
"Rivka is trying to avoid gentile kids throwing water balloons at each outside of the McDonalds, so she employs the Yeshuffle."
"Shayndie's gemara class starts in 3 minutes so she is yeshuffling as fast as she can."