Has to do with them being stamped out of flat sheet metal. The side the punch hits first is rounded over slightly and then other side has what is basically a small burr around the edge. The burr or sharp side goes against the non moving area. Or similar to using a washer under the head of a bolt, the smooth side goes against the bolt head and the sharp side goes against whatever you are bolting.Sharp flat edges on washer and snap ring face out away from the race.