Arkadia is a refugee.  It is where the last survivors of a once powerful race of humanity came, and very few have ever left.  It is such an alien world, figuratively speaking of course.  It is too vast to occupy, and has too few resources remaining to be worth it.  The Arkadians lost their interest in the outside worlds, and found a new one that no one else would be interested in taking from them.  And they keep telling themselves that they like it that way.  I wonder.