In regards to that I"ll put it like this: Dhampir drink blood. Draug devour corpses. Alps eat nightmare and Vetala rot bodies. [u]They don't need to.[/u] It's not like they'd wither away if you put them somewhere where they couldn't and left them there for years. So the act of a Dhampir consuming human blood isn't motivated by thirst or survival but rather an act of compulsion. Vampires don't decide to act on it, they are impelled to do so by their curse. One of the reason sticking around to watch over any loved ones is a recipe for disaster.

To simulate this character sheets will include a list of rock-paper-scissors choices that represent your ability to stave off this compulsion--occasionally rolled against when giving in would be less than ideal (Like interrogating a witness, escorting a VIP, etc)

In a nutshell it doesn't nourish them and you'd only enjoy it if you were that particular shade of fucked up to begin with. At the very least the fact that it's not a choice is unpleasant.