Quote - Another point is that to be a model physically correct it doesn't mean that it looks correct, it only means that the model obey the conservation of energy and follows the laws of physics.
We must define which are our objectives, what we want to do.
There are many application where 3d engines can be used, architecture, design,engineering, marketing, media, art
For example, radiosity is excellent for illumination design of interiors, but if you post an image in the gallery soon someone will comment that you did the image without shadows, objects are floating above the ground and so on. People want to see shadows even a well designed interior illumination produce no shadows.
You see a beautiful rendering of a house, it is marvelous and the image is excellent, but you and nobody lives in this house and nobody knows where it can be found.
A beutiful rendering of a crystal ball and a metallic sphere, is beautiful, but have you ever found in your life one that looks like that?
Beautiful images, but are artificial and have no life.

Don't turn to a philosophical consideration. Mutch of us do things just because we can. Because it's nice, because it looks professional at the end, add your preferred reason.

We don't ask why. We ask how. And then we do. 

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