This question was in the Washington Post's old "Why Things Are" column. I don't remember the details, but basically telephone keypads (which came later) were designed to be the opposite of keyboards because the phone companies were afraid people used to using the keyboards would just type the numbers too fast. Now of course everybody can use both quickly.

It's worse than metric vs. English systems. The U.S. is the only major country that is still using the English system. We will eventually go metric because the hassle of being out of step with the rest of the world will eventually become greater than the (short-term) hassle of changing over. But I think we will have different keypads for computers and phones forever.