[Guest]

Well, blur is one of depth perception cues; so it's ok, you are not alone - there is the whole big science about that .

 

A.

 

Well, while lenses do have limited DOF, only photography really has made an art out of it to isolate subjects, so to speak, i.e. the large sensors and lens physics (aperture) automatically forced photographers to work with that. Camera obscuras (pinhole) of the old school painters didn't have that limitation, so you don't see any out of focus blur in their paintings ;-)  

And the human eye really is mostly looking at the world all sharp, because it focuses constantly on what we are looking at, and it has a pretty good DOF. Most of depth perception comes from our 3D view and knowledge of our surroundings, not from blur. But blur can replace that to some degree in 2D images.