"I mean, even if your kind of vampire happen to all be saints, which isn't the case, it could interact really badly with my kind, or with some sort of demon, or with brain-melting magical powers, or something like that. I'd be tempted to take it for myself but I'm already upgraded and don't want to fiddle with that lest that interact horribly - a lot of things in my world are just sort of disposed to be horrible - and I can't make avoiding death by old age a particularly high priority until I'm sure I can do better than all my predecessors at not dying of violence."