One of the most realistic post apocalyptic movies

No hoards of zombies or roaming cannibals with a lot of violence.

A bunch of ppl with different backgrounds and personalities trying to get along and survive together.

Though I don't get the ending where Benjie decides to leave and Becky a hard core Christian decides to leave her husband and have premarital sex with another.
And they are leaving the safety of the cabin?
With all that weed?