It is an oversight that you can't reanimate full skeletons you find in dungeons, I give you that. Any other argument you are making is not viable!
You can. I've done it. Not all skeletons, but many.
A pure necromancer raises the dead, steals life, instills fear and rage, controls demons, uses poison and disease.
You can play a "pure necromancer", but it requires conjuration, alchemy, illusion and maybe a taste of destruction and a blade.