From a Newsweek interview with Steve Jobs: (emphasis mine)
Q: At one point you were saying, “When our customers demand it, that’s when we’ll consider interoperability.”
A: Nobody’s ever demanded it. People know up front that when they buy music from the iTunes music store it plays on iPods, and so we’re not trying to hide anything there.
You hear that, everyone? We never demanded it. All those wild discussions, all those Winamp plugins, all those alternative OSes, all those DRM workarounds, completely ignored, because customers of well over 50 million iPods never demanded interoperability.
What pains me is that Apple has already won. They could go for interoperability now and still win, maybe win even more, because having products as good as iTunes and iPod support other formats is a customer magnet. I want to use OGG Vorbis, FLAC, DivX, Windows Media. I want iTunes to speak your crazy moon language. But most of all, I want Apple to acknowledge that I want that, beyond hiding icons.