I'm not even talking all those traps, etc. I'm just talking basic lighting. Every dungeon is lit. Even the Underdark.
Dungeons are meant to be subterranean and pitch black. An owlbear cave should be exactly this, as should the necromancer's lair, the basement of the goblin lair, the spider lair, and especially the Underdark.
It would also make rendering easier on computers if I can't see more than 60 feet as an elf or half elf and more than 120 as a Drow. The game wouldn't have to have these massive, subterranean views where you can see for miles because of all the glowing plantlife.
