M.M.
This custom of wrapping the abdomen after having a child gives the woman support (that a girdle would give) and also helps to flatten the abdomen. While this practice still works, it is not as popular as it once was and it would be a lot more convenient to just wear a girdle. Keep in mind, though, that this is more or less a way to try to altogether avoid or take short cuts to exercises that tighten the abdominal muscles. It may help, but is will not solve the problem like regular exercies will.