Well sort of but no...
It is so you can launch a specific game directly from the dashboard, but I highly doubt anyone is looking to do this for every rom.
Say, for example, if you really love Super Punch-Out, then command line launching allows you to set it up so you can launch straight to that game straight from the dash, like you could any other xbox game or app.
It would be so I didn't have to load up some other gui, just to launch the one game I really want to play.
I personally have an arcade machine with an Xbox in it, and there are a few SNES games that I'd like to add to the list of immediately accessible games. I have the dash set up perfect for easy access to many games, and the dash is nicely skinned for the machine. It is nice not to have to load up a totally seperate interface for selecting stuff.
[EDIT]
Here is an example of what I am talking about. In the background I have a video of an arcade playing, and on the arcade machine, I can select a game, while the marquee changes to the game's title, and the arcade machine's display shows a preview picture or video.

What do you have to do to launch an indiviual game with an emulator that supports command line launching?