The simple explanation, is this ; First, its the "character " of the genre. It was adopted from the way that Cubano ladies walked ( hip swinging actions ) . And, there are 2 competing theories, on HOW one achieves the CM. One is a straight leg (Intern style ) before weight is transfered, the other ( American style ) stepping on to a flexed knee before weight is received . And it really never was about aesthetics, more about practicality for those ladies who, as they carried baskets upon their heads, would walk, kinda tentatively ( with a flexed knee ) . And that, is how "we " walk, in normal everyday usage .