Actually, they don't. And that's the problem.

The bigger problem here is that we're breeding sexually incompatible human beings, and vampires are to blame. I can see a time coming when the birth rate is going to precipitously decline. And what that means is that vampires are going to run out of food. But if Charlaine Harris, Laurel K. Hamilton, Stephenie Meyer, and all the others are right about the souls of their emo, Goth, velvet-wearing, crybaby vampire spawn, then maybe some kind of mass, Kurt Cobain-inspired, "You'll miss me when I'm gone," specieswide suicide is what vampires have been after all along.