Reason for the darkness?

[LuckyBlackCatXIII]

I always thought he kept it dark to somewhat conceal his servants (I mean, you think Daniel would have noted on just how the 'skulking' servants looked if he saw those things) though that's a pretty weak reason, I'll admit.

Or maybe Xander just likes the dark? (and will burn to ashes at the slightest inch of sunlight /shot)

This is an interesting topic, I'm glad someone brought it up!