I've watched some videos by an artist going over character designs from various video games, like Marvel Rivals and Pokemon. Actually there's a lot of people doing those sorts of videos now, but she's got some actual schooling and brings up things like color theory and shape meaning. And it's the latter that matters here.
Her mantra is that rounded curves are friend shaped, rectangles signify strength, and triangles mean danger. One villain after another has pointy bits all over their design to drive home that this is something dangerous and menacing.
So I'm not surprised that vampires often get pointy ears to go with the pointy teeth, the better to show that "This is a predator, beware of it."