thesheeep
Arcane
This is the first time I've ever heard anyone claim this as a general rule.they are also asexual.
At least for VtM / WoD.
Sure, there are mythologies around in which vampires have no sex drive.
But I have yet to see a single product for VtM / WoD, including rule books, in which vampires are not very much sexually active (and actually sexually diverse, always have been in VtM). Of course, some aren't interested in sexuality. Some are certainly asexual, but by far not all of them.
Vampires are just humans with superpowers, really, they don't change their entire being and personality once embraced - except of course for personal developments over time (and with much more time available than a normal human).
Someone who enjoyed sex while alive won't suddenly have zero interest in it after the embrace - even though they might indeed have trouble getting hard or wet (and that's where skills/feats come into play in some systems or with some DMs).
I could see vampires gradually turning more and more asexual over time, as a result of either their lack of functioning body parts and/or a "been there, done that" lack of interest.