Answer. Posted on Wednesday, December 24, 2014.
If you look at the objects that seem to us shining, it becomes clear that the shine is a reflection of a bright light source from the object that reflects light well. Let’s compare how light reflects from the cube and from the sphere. Each face of the cube reflects light in its own direction and in order to notice that the cube glitters, we have to stand at the place where light will be able to hit the eye. The sphere reflects light in almost all directions, so no matter where we are, we are likely to see the shine.
To summarize, it is not that round objects more shiny, they just shine in almost all directions.