iPhone (and iPod touch) feature request

I really would have thought this would just work. I have my music collection in iTunes on my Mac Pro. I can use my MacBook Pro, for example, to stream that music over WiFi and play it somewhere else in the house, albeit over laptop speakers. I just plugged my iPhone into the (ageing and apparently incompatible) Bose SoundDock in the kitchen, and, unless I'm mistaken, there's no analogous option for streaming over WiFi to the iPhone. I don't see how there could be a technical or licensing impediment to implementing this for the iPhone and iPod touch—is there?