At first glance, one might be tempted to wonder why so many of the vampire legends in Natsuno's movies turn out to be true of the Shiki. However, when you consider that vampires actually exist in the Shikiverse, it makes sense: at some point, some people would have had to have actually met real vampires, and created the popular myths and legends about vampires from their own experiences.
So, it's established that most vampires are buried before they have a chance to rise from the dead. It's also established that the vampires can't dig themselves out of their own graves. Imagine what it would be like to rise up as a vampire...and have no one come to rescue you at all.
The series essentially goes out of its way to dismantle preconceived notions fans of vampire series have about how they would handle themselves in a situation like the one presented in this story. So you think you'd alert the villagers to the threat of the vampires? Sorry—chances are most of them won't believe you, or will have a vested interest in keeping the story under wraps even if they do. Think you could take the vampires down all by yourself? That's what Akira thought too, and look where he ended up. Oh, but you say you'd be the good vampire who wouldn't kill anyone because you're so nice? Toru was nice too but it never stopped him. And even if you did refuse to drink blood, you'd just starve to death or be killed by someone in charge of making sure you drank blood. The wide variety of characters, at least one of which everyone can relate to, and all of whom get dragged into the violence, reinforces this point: the series is essentially passing judgement on how you would react. It's implying that you would either kill or be killed, and there would be nothing you could do to prevent the violence around you. Which is quite a terrifying thought.