The enogram itself is based off of a, in the words of the amazon description for to day's book, in an ancient personality typing system. The other interesting part about the eneogram is that you basically pick your own type. You pick the one that resignates with you. So maybe that kind of leads to it. Maybe productivity books and business people weren't a thing when this existed,. so they just flew under the radar and didn't have an opportunity to say, this is the way things, brandit. Brand it their own way.