Why do most of the animals and other creatures have only two eyes?

Two eyes are the fewest number of eyes needed to see in 3 dimension (3D) or stated differently two eyes are needed to provide an animal with depth perceptions. Depth perception allows an animal to gage distances between objects. This ability is essential for an animals survival, both as predator and prey. My answer explains why most animals have at least two eyes but not why only two eyes. Evolution or nature follows (for the most part) the "keep it simple" rule. Since two eyes are all that is needed to view the world in 3D why have more than two.