I haven't picked up the issue yet (I'm a trades guy) so take this comment as you will:

Because, as an evil ex-Watcher declares, "the vampire is regret personified. A hunger for life that's been damned to never be satisfied." That's why vampires eschew Hanselstadt.

It's entirely possible that the evil ex-watcher was full of it. Just because a character says something doesn't mean it's acurate--even if they're super-knowledgeable types.