LaWally covered it great. Here's how it's applied for me...
In the living room, the family might be watching a 5.1 surround sound movie on the

TV. Out on the deck, I might want to pump some stereo audio from the SATT receiver to listen to music out there. The receiver is built to do this (play both sources of audio at the same time) but it needs analog in for zone 2 (digital in doesn't work).
The desire for

TV3 to have it goes like this: family is watching surround sound show via the SATT receiver. I'd like to play my favorite iTunes playlist on that deck. This works just fine for me now because I kept the

TV1 (with analog out).

TV2 couldn't work this way without some kind of added hardware.
Many people see

TV as some kind of video player- especially an iTunes store rental video player. In fact, it's many traditional pieces of hardware rolled into one- and generally done better. It was not that long ago that I owned Sony disc jukeboxes: one for the DVD collection and one for the CD collection. Now all that resides in iTunes and all can be played via

TV. Sure, it's pretty good for video playback but it is also a good audio device too (generally much better than that old CD jukebox hardware-- shuffling the whole collection on the jukebox meant long delays between songs while one disc was swapped for the next).
While HDMI and optical make sense for preserving surround sound audio associated with movies & TV shows, good old analog audio is still a pretty good way to move stereo audio (all our music) around. Sure, technically pushing that through an optical cable is maximizing the preservation of sound bit for bit, but if we've embraced compression vs. CD, we're really saying we're not that hung up on purist quality of audio and probably few of us could tell the difference of whether an audio track got to our receivers via optical digital or analog cables anyway. As I understand it, the hardware is already on the iPad-based board so it's not like they have to go way out of the way to make analog audio out an option. And a mini-jack would easily fit into lots of empty spaces for it on the back.
All that said though, for a subset of us, it would be a nice feature to resurrect from gen 1 to gen 3. Especially for multi-zone receivers, it certainly has a tangible application.