Why would you install Panther on an iPod?

Am I missing something good here? I am getting a 20Gb iPod with the Cram & Jam promo with my GF iBook; and I know you can use the iPod as an starting disk right? But what is the use of this?

Let me squeez more juice of my iPod...specially now that it has 20GB instead of 10GB. Cuase to be honest I have 5GB of music more or less and the rest I was going to use for storage and transfering large files...but what use do I have of having the iPod as s startup disk?

Thanks.