thats because no one targets a mac. Macs make up a very small percentage of personal pcs usage in the world and even fewer use them in a corporate environment. Its not htat they are virus proof because they arent. Hackers and virus creators are extremely bright and realize that targetting a mac is rather dumb when they can target a windows box that could potentially land them a nice score. A Mac is security through obscurity.
Jesus Ive spent far too mcuh time studying lately.