Here's the difference: We've got a huge group of people here with expertise on how to deal with vampires and hunters. We don't have that kind of resource to deal with demons, or witches, or anything. And they -- haven't been making trouble as a group. [ apologetic smile. but, sorry. Diva's actions and Sam and Dean's actions and even Rido's actions from long ago do matter here. ]
"Why vampires? Why not other supernatural beings?" ...Because we can do something to help with vampires. If we had fifteen gods and ten specially-trained god-hunters here, I might well be making a group focused around their interests.