Society crumbled under the weight of interstellar distances.  Every station was alone, isolated from all others.  Communication was much more common in the form of bullets than any other form.  And why shouldn't they?  A conversation between starships would take hundreds of years at minimum.  Personal relationships gave way to cold millitary alliances, which in turn gave way to bitter squabbles over distant resources.  No diplomacy could withstand the brutal efficiency of these war machines.  Every station within 1000 light years was a potential threat, and allways they watched each other through perfect optics.  What choice did they have?  They fought.