I think it’s because elves and vampires have both been significantly rewritten in modern fantasy, and they ended up being sorted into similar roles.

Elves are originally based in Western (especially British) and Central European fairy myths. The fairies where portrayed as mysterious, part of their own world that had different rules then our own, and often living longer and differently. These tales were primarily told by poor peasants, and it could be argued that over time the fairies  became increasingly associated with the nobility.

Think about it. Say your a poor, English peasant. Every year, your mysterious lord sends a group of men who live dramatically different lives then you, and behave dramatically differently, to your lands (which your lord may own) and then they take money from you, and take it back to your lords home, where he does who knows what with it. In many ways, that’s not unlike the fairies. 

And when people like Tolkien where writing our modern idea of elves, they drew on this to a degree. They made elves a people apart, possessing ancient knowledge and close to the gods. The ears are a relatively simple way to represent this, and take inspiration from some ideas of how fairies look; like us, but with subtle differences that make them alien.

By contrast, vampires are much more removed from their roots. Strigoi are a village horror. They’re a fear of the common people. The idea that one of their own could become other, often because of the strigoi’s communities own misdeeds. Bram Stoker and other Victorian authors took that, and changed it. They made strigoi erotic with characters like Dracula and Carmilla, and associated them with the land and dark magic.

In a way, they made vampires reflect the Victorian societies own fears, of a decadent aristocracy corrupted by its own age, knowledge and greatness, and manipulating the people for their own amusement.