The caves have a mean streak to them. Going deeper feels less like a heroic expedition and more like slowly realizing you were never meant to come back. Eleven layers keep the pressure building, while the unlocked Full Game gives a little breathing room without taking the bite out of the survival side.
What sticks with you is the ugly truth behind the job. The cargo is only the excuse. Someone decided these prisoners were expendable, and now the player gets to find out just how far that decision goes.