Help me understand Smoothness property of Standard Shader

My question is fairly simple - Why doesn't a smoothness value of 1 make my object more/shiny or reflective? Instead it appears to make it completely flat (see image below).




If you compare a smoothness value of 0 and 1 (shown in left and right images above), they appear similar however the smoothness value = 1 appears to give a darker, IMO more realistic representation of the material color.



The same applies with an image texture. If you leave the smoothness value at 0, there appears to be a white haze over the object (above left). However, when you set smoothness to 1, you get a a more realistic representation of the colors in the image texture. Why?

I simply do not understand how this property is supposed to work. I have also read that using the Specular setup and changing specular to black may be the best approach for flat, diffuse materials.

Any insights here are greatly appreciated!

 

A smoothness of 0 is basically chalk powder.
A smoothness of 1 is basically a theoretically perfectly mirror. However if you don't have a baked reflection probe (either a default one from lighting panel or by placing a Reflection Probe in the scene) it'll look very odd as it won't have any reflections.

Real world objects are somewhere between 0 and 1.

 

Thanks, that helps alot!