So I was thinking, why are all the zombies and skeletons and wights and things in the vampire counts undead army all humans?

Surely if they killed a load of skaven or orcs, they would simply raise them from the dead instead. This lead me to thinking I have a crap load of models I don't use or care about any more, is there anything that says I cant convert my own zombies and wight champions?

I did read somewhere that the reason there aren't any non-human vampires is because all the other races live for such a long time anyway/resist the magic but surely that doesn't stop them from being raised from the dead.

Anyone got any clues. Pretty interested on this topic.