I don't know why Apple hasn't done this natively yet. Seems like a no-brainer and something a lot of users will find super-useful. I know I would, but not sure I want to install a third party app to have to run in order to get this done.
This makes Apple look stupid so I can't see them approving it. Hopefully, the bad press will at least get them to finally enable the feature themselves. There is no technical reason they can't do it. They just want to save certain things for future models so they can push you to upgrade (i.e. why wasn't cut & paste in V1.0? 2.0? It wasn't an accident that's for sure).
Other things that should be obvious that Apple hasn't supported thus far:
-Ability to play iPhone/iPod songs over Airtunes straight from the device on your local network (to work with Apple TV and Airport Express units). This should be a no brainer, but it hasn't happened yet because Apple wants you to BUY a dock for your stereo instead so they won't support it.
-The reverse should be possible as well. You should be able to access your shared library remotely across your own network like a regular Mac can do including watching videos on the device that are compatible (helpful if you have large libraries and want to hear a song that's on your home server when you're in your backyard or whatever without having to copy it over first.
-Lyrics in the "Remote" app like it already displays for songs stored on the iPhone/iPod (mystery to me why this hasn't been included; I've sent feedback asking/suggesting the feature and they ignored it, it seems).
-Visualizers for Apple TV and/or the iPhone/iPod Touch. iTunes has it, so why don't these devices? They're more than capable given the basic displays iTunes has in it. Slideshows are OK on AppleTV, but why should I have to boot up XBMC just to see a light show on my big screen projector?