And this I think directly related to the OP’s question. As GuanoLad pointed out, there’s no real lack of “focus” in in the natural world as seen through human eyes; ignoring extreme edge cases, whatever you’re looking at is in focus. We think of distant things as getting fuzzier, but that’s not the same thing as focus (at least not in the lensing sense). The background of Mona Lisa shows the effects of haze and distance, not a lens effect (note that the colors wash out compared to the foreground, too, which doesn’t happen with misfocus).
Computer graphics started going through this phase about ten years ago where “photorealistic” images started incorporating a digital lack of focus at certain distances, to emulate focal length. It’s an interesting cultural curiosity that we consider an image to be MORE real if it contains the faults of a camera’s viewing system (focus) than if looks like the real world does to our eyes. We’ve grown up with photographs, and now we expect our digital images to look more like a photo than nature!