Yeah, aside from churches being 'holy ground', I don't think there was much stock put in 'religion' one way or another. I think Joss mostly went with 'general vampire' lore.
Whereas, in
The Dresden Files (books), religion and belief are hugely important to how things work.
Just depends on the mythos you're building, I guess. Plus, Joss wasn't so big on 'preaching' to the audience as 'demonstrating by metaphor'.
