I'd say dark areas should be absolute black, otherwise you end up like Doom 3 where people just turn up the screen brightness to crazy levels to see in the dark. Terraria's darkness goes down to absolute black and that keeps things hidden on the screen until the player gets a light source to it. Of course Terraria's light sources don't cover nearly as much screen space as AVWW's...
I understand the sentiment, but a couple of points:
1. If someone wants to do that, who does it hurt?
2. Turning up brightness in the doom 3 sense is not possible, as this is not a true lighting model. The only thing you can do is increase monitor brightness. I play at max monitor brightness already, and I can tell you that it's not a playstyle that anyone would validly be able to choose for very long.
3. In general we structure the game and enchants so that you don't have to choose between a light source and something more useful. Most of the time you can find a light source on something useful if you look long enough, and if you don't wind up finding that, then you can still use ball of light and similar instead for a while.
4. Increasing the darkness values doesn't have the effect you'd think, because of the way that we are creating the darkness. What we're doing has 0% in common with lighting models in most games -- rather, it's a graphical trick. Various top-down zombie games that simulate "line of sight" type darkness also use graphical tricks to do their darkness, for similar reasons, although their methods are a bit different from ours.
Thus comparing it to something standard like doom 3 (which uses actual GPU-style lighting) is kind of irrelevant, and talking about making it darker actually makes it more soupy and strange-looking rather than just making it actually darker. See early videos of the darkness when the game was still top-down for an extreme example of what I mean on the soupy-nature.