Just rewatched it. I guess I've always knew this, but it is one of those things you don't realize until you're told, but the writer stated that these are all lost souls with no memories being experimentd on the parasitic aliens, and that it is like a purgatory. Tapping into Descarte with the tabula rasas (blank slates/no memories) of said "lost souls" and Kant with his theory of pre-established knowledge at birth, the writer wanted to present the fact that we are more than the sum of our memories. That there is something more. He went on to say that we are born to be who we are: the good sister, the murderer, the leader, the artist, the loner. Kind of bleak, but interesting.
Also, the writer dreamt up The Strangers. So that's kind of chilling.
I always considered that the world had ended and that The Strangers took over, perhaps destroyed it. But there was always the fact that they could've just abducted these people. Maybe from a different time all-together. They chose that timeframe of 30s/40s because it was a Depression-era, makes the subjects docile. Really interesting layers of the film that you can have entire conversations about. Just love it. And why this is easily one of my favorites. Top 10, easy.