Because
most people take photographs standing up with the camera at
head height, and this is the viewpoint we most often see photographs
taken from the images produced from this view point are often predictable and lack visual impact.
However
when we lower our body position the view point alters and we can
present images with a more interesting perspective.
It
is possible to position the camera even lower to extenuate the
perspective.
Or
we can position the camera above the subject.
Here we see two photojournalists working from two
quite different viewpoints.
Here we see three quite different camera positions.