Now I only have to solve the mystery of why numeric/calculator pads are inverted compared to phone pads and I might see some logic in keyboard layout...
It might have sth to do with sequence of letters in alphabet i suppouse :) It would be strange to have "a" letter at the bottom :> But i'm just guessing. That would be the answer for question why phone keyboard are inverted compared to calculator/numeric :)
So answer to your question might be ... numeric is much older than phone keyboard and thats how they developed it and thats how it still is.