This new feature removes a requirement to "hack" the AppleTV to play non-supported audio formats, since you can set that up on a Mac and blast the audio in agnostic format to AppleTV (and Airport Express units) around your home/office.

Just in case someone wanted to use a format created by two college kids to broadcast music on their own internet radio station hosted on their schools intranet.

This could also streamline the family room/media room since you don't need an Airport Express stuck in an outlet with long cables snaking around the baseboards to get to your 5.1 speakers. Note that AppleTV can now do true 5.1 audio so it all fits together with one thin little gray slab with an Apple logo on top (and not Microsoft, or any random hardware ODM).