[@Genon]: Well... Sapient undead are [i]incredibly[/i] rare, it's almost impossible to actually get one intentionally. Which is why there's not more of them.

Additionally, necromancy is considered an abomination by the church(at least, the raising the dead type. There's [i]some[/i] offshoots of it that have medicinal uses and communing with spirits of the dead isn't viewed poorly), so someone who could even attempt it just being around for the king to ask it of them is pretty much impossible. Let alone the king asking them to begin with.