Every beginner in photography does one mistake which professionals don't like i.e. keeping subject in the center of the frame. He must have been bombarded of advice for not doing that mistake again by senior colleagues.

Centered place in the frame is considered having less visual attention of the viewer. A subject in center divides the frame equally & may confuse the viewers eyes where to look at? This offers a less visual weight to the subject.As soon as subject is moved from the center of the image starts to get a dynamic feel from a static. The golden point according to very famous rule of composition which is Rule of thirds.

In this image I have placed the egg in center of the frame but is it really not visually interesting? The answer is yours since it is going to be subjective. I think dividing the entire frame using shapes of circles helps the viewers eyes to recognize the subject with an ease (Ref: Gestalt psychology). So composing the egg in the centered portion doesn't matter to much, in fact it is catching the viewers attention without loosing interest. If the subject was only egg then there will be enough space to divert viewers eye in entire frame resulting in poor composition.

A centered subject can also be made interesting by using virtual lines leading to the subject. It will avoid the viewers eye to wondering everywhere unnecessarily while guiding it to the subject of interest.

Your feedback will surely help. Kindly correct me if you find anything wrong with the discussion.