For translation, you have the grammars of different languages. Only a human who is fluent in both languages can create the set of rules. And how many rules are needed? The good thing is that many different human experts can all contribute to the same set of rules. Once the rules are written down, they won't be forgotten. A good translation program is probably many man-years of work.

The real issue is this: can a set of rules translate every sentence correctly? Or are languages too complicated?