Depth of Field being visible is an artifact of 2D screens & prints. Our eyes do have depth of field, but when we look straight at something they very quickly refocus onto that thing, so it's often very hard to perceive. With a static photograph or picture on a screen we can't refocus on what we're looking at within the picture automatically.

It's not that our eyes don't have depth of field, it's that they operate differently than fixed photos or pre-set DoF effects in a game.

Blur is completely natural to human vision, to any kind of vision. Look far away while bringing your hand close. Blur. Now look at your hand. Everything else goes blurry. You can even unfocus your eyes while looking at something. Now everything's blurry.

Damon Albarn would disagree.