|MadSci Network: Science History|
I don't think that there's any "great conspiracy" afoot here. I'd
guess that the reason numeric keypads are different on computers and on
telephones stems from tradition.
You see, mechanical adding machines and cash registers were the first objects with numeric keypads. Having used one or two, I can tell you that the numbers were always arranged with the lowest at the bottom and the highest at the top. When electronic calculators came in, they kept the arrangement similar so people who were used to the older style would have less trouble adjusting. And computer keypads are based on adding machine layout via four-function calculators - primarily because the people who use keypads most often are data-entry people, those who used to use adding machines.
On the other hand, rotary telephones started with "1" in the upper right corner and moved counterclockwise around to "0" in the lower right corner. When touch-tone came in, the keypad was apparently designed in a similar fashion, with the low numbers at the top. The arrangement was changed to run left-to-right because that's the way Westerners are used to reading things.
Try the links in the MadSci Library for more information on Science History.