The problem with a default place for saving rackspaces is that users may have multiple rackspaces with the same name but slightly different content, depending on the gig. I certainly have this myself.
For example, I have a rackspace called Piano which I use in gig files that are in the context of a band. But I also have a rackspace called Piano which I use with gig files that are for solo purposes. The difference is mainly the EQ for the piano, in the band gigfiles, the bass is reduced for the piano so as not to interfere with the electric bass player.
If everything was saved to one place, then it would be far too easy to replace (and lose) rackspaces. The user would have to have extra discipline, perhaps with extra subfolders, to make sure to not overwrite rackspaces.