Voted other because that poll is really, really unfocused. It also doesn't cover why you zoom in the first place: To mimic focusing by constricting your field of view while enhancing the target location. Since they can't actually do this with a computer screen, they have a zoom. Just blurring the edges(as was suggested) would pretty much do the opposite of focusing on a spot. It would be equally hard to make out, while you'd lose peripheral vision, just like if you had been drinking heavily. Natural selection would have a field day with anything that used that method of spotting things.
Try looking at something, then shifting your vision to stare at something nearby. The apparent resolution(clarity actually) increases dramatically when you do that. Now someone explain how to make that happen on a monitor and have it work with your human eyes that are already doing this as you scan the screen. Without vision tracking hardware, it's impossible.