Vampires did get heavily nerfed once all the realism players that bought the Vampires pack started complaining about Vampires in their games a lot...
I don't know why EA listened to them, or why they even bought Vampires when they didn't want to play with the occult, but they were making a big fuss in 2017.
I wouldn't be surprised if it takes a crazy long time for your own Sim to do it, and I definitely don't see any townie vampires autonomously drinking from other sims. I never even get any breaking into my home anymore. I used to get regularly stalked by Caleb and now my yandere boy is ruined. :(
