It is often thought by the general public that the primary aim of good design is to make things pleasing to the eye. This is a misconception for which designers themselves are partly to blame. By showing pictures of their work and talking endlessly of aesthetics they seem to ask to be judged simply by the appearance of things. Indeed it could, and in my view, should be argued that aesthetics has always had a more functional role than that of 'entertainment'. It is to give things meaning.
Good design enhances our understanding of an artefact.
If we take this view of design we can see immediately why we need good design in presentation graphics. By designing our output well we can improve the way it communicates. Enhancing meaning Good design, then should provide 'affordance'. In contrast, a pull handle fixed to a door that is meant to be pushed does not provide affordance. What the handle appears to say is 'Pull' Tha action required is 'Push'.