User blog comment:Nick tanico/Umbra Origin/@comment-89.241.78.78-20150113210442

The Umbra had a high body count during the Clan Wars, which is how the Witch Hunts went by so swiftly. There's also 500 years between the end of the Witch Hunts and the present, giving ample time for more witches to die.

Plus, given how rigorous the training was, I doubt there was a high amount of Umbra, anyway.

Though we do have mentions of Witches (unknown if Umbra or not) from other countries, which could be a good plot point.