Safari and Quicktime are available in Windows, but does not have as many codecs as WMP. It would be great to have Perian for Windows, because without them it is nice to have Safari if there are native Windows alternatives.
Your point, even though you are not the OP, is that a player can play its native formats without additional plugins? What's the surprise in that? Now on the other hand, let's see WiMP take plugins to play formats that it struggles with.