FOSS gamedev and creative worlds

Strange question... but why no complete darkness in caves? There is no light sources, but I can see stuff inside.
Is this even possible to make it COMPLETE DARK so even increasing gamma will not help you? Why not make it fully dark? It will be much more challenging and fun (while also addressing this -> viewtopic.php?f=6&t=13511)
Example of current blackness:

The two issues are not related - one is fog colouration, the other is brightness.

Also not everyone finds that fun - which is why there is a gamma setting.
My screen brightness is generally low, and when I get stuck in a cave without light, I find blindly flailing about with a pickaxe for coal very irritating.

Also complete darkness is used at night, which is supposed to be moonlit - changing this to a higher light level may reduce performance.