Why are there so many survival games? And why do we love the pain they bring?

Remember when Day Z was a fresh, exciting new spin on the video game corpse-grinding simulator? Remember how exhilarating it was to discover that the undead were just one, ambient part of a wider ecosystem of endlessly unpredictable pain? Remember how thrilling it was to find that the focus of the game was not the simple chopping through of rancid meat skittles amid various decaying towns, but rather