Board Thread:Warhammer 40k General Discussion/@comment-6078851-20130130174042/@comment-3258762-20130218203539

Actually, the Emperor did not only create them as generals, or else he would not have imbuned every primarch with the administration skills to rule a bureaucratic society (Even Russ was a master of politics, Angron less so because his Butchers Nails changed him to the core)

The Emperor created the Primarchs to be perfect, probably to help govern and expand the Imperium when he was working on further scientific experiments. He wanted a council of humans, astartes and Primarchs to rule the Imperium in his stead, but in the end all that became of that was the High Lords of Terra since no Primarch managed to see the end of the Great Crusade, so to speak. They had a purpose, and that was to be the best thing humanity could have in all aspects, where the Imperium could no longer be drawn into foolish wars of extermination because of the bitterness and jealousy of a common man.